Delayed throttle

[Bitsyncmaster]

My friends DeLorean has a cold engine delayed throttle response. When the engine has warmed up the problem goes away. Here is the video.

https://www.youtube.com/watch?v=6eddnXa6F58&feature=youtu.be

Of course I've never seen such a thing on any engine I've ever worked on. The engine is always warmed up when he brings it down to my house. I just guessing something is binding up with the fuel distributor when cold since he does not have this problem once the engine has warmed up. Here is his warmed up video.

https://www.youtube.com/watch?v=44PfHKjexKs&feature=youtu.be

It's hard to fix these problems via email.

[MikeWard]

I'm assuming all vac pipes etc are routed correctly? There is a good guide for testing the routing without stripping the intake off, over on the eurotec forum: http://www.deloreaneurotec.uk/viewtopic.php?f=17&t=4619

If Vac pipes are all ok, then it sounds like a potential problem with the CPR (WUR) to me. He would need to do a fuel pressure test to confirm. This would also a good time to check the primary pressure of the system, which should be between 5.2 to 5.3 bar (75.4 to 76.8 psi) for a stock exhaust system.

If the pressure is under those figures, it will need to have special shims added in order to restore the system back to oem spec. These are available from the delorean club uk store if required: http://www.deloreanclub.uk/fuel-pressure-regulator-shims.html

[81dmc]

Does the plunger assembly move freely when revved cold? If it does, refer to post above.

[Ron]

Assuming all of the basics have been checked, I'd suspect a vacuum leak because of the spit-back/popping, which indicates a vacuum leak (lean).
If it goes away when warm, I'd suspect the line(s) from the Thermal Vacuum Switch to the WUR/CPR first.
Then:
"Small" Vacuum leak in general.
Thermal Vacuum Switch (hung at warm position/not getting supply/etc)
WUR/CPR (defective/pressures off).
Delay Valve

[Bitsyncmaster]

Assuming all of the basics have been checked, I'd suspect a vacuum leak because of the spit-back/popping, which indicates a vacuum leak (lean).
If it goes away when warm, I'd suspect the line(s) from the Thermal Vacuum Switch to the WUR/CPR first.
Then:
"Small" Vacuum leak in general.
Thermal Vacuum Switch (hung at warm position/not getting supply/etc)
WUR/CPR (defective/pressures off).
Delay Valve

He has checked the vacuum going to the WUR and it seems good. He also changed the WUR. This looks like something you would never see with a carburetor engine. With a carb your engine would die when you punch the throttle with no response. I'm really thinking it's something with the FD or the linkage in the air plate just binding when cold.

[DMCMW Dave]

I'd vote for sticky fuel distributor plunger.

[DMCVegas]

I had this same exact problem. In my case, I had two problems that contributed to it:


Craptastic aftermarket "performance" ignition wires that were leaking and arcing out to the side of the sparkplug wells.
A clogged fuel injector.


I couldn't point at one directly per se as the cause, but both were remedied at the same time and resolved the issue completely. One cylinder running half-assed because of a lack of atomized fuel is bad enough. But on a cold engine, it's practically dead. The excess amount of unburned fuel was going downstream and hitting the O2 sensor. That would cause the LAMBDA system to lean out the mix (precisely what you DON'T want on a cold engine), and then it would stutter more. Then of course it over corrects itself and enriches the mixture too much, and then you stumble again. A little less of course, but so it continues until it balances out. It goes through the exact same cycle as a vacuum leak, and causes the same symptoms.

But once it warmed up the other cylinders could take over for the bum one, and it would have great throttle response again in a few minutes. At that point the fuel economy sucked, but it still ran decent enough.

[Ron]

He has checked the vacuum going to the WUR and it seems good. He also changed the WUR. This looks like something you would never see with a carburetor engine. With a carb your engine would die when you punch the throttle with no response. I'm really thinking it's something with the FD or the linkage in the air plate just binding when cold.That be the case, I'm with the other Dave lol
It sure sounds like it's going lean somehow.

fwiw, I've seen a lot of carbed systems spit-back/pop and recover w/o dying when the choke was off (lean/stuck open) and act fine when warm (of course).
Not many, but some with small vacuum leaks...

[81dmc]

Tell him to remove the mixture unit and carefully clean the plunger assembly. While he's in there, he probably should clean other things as well.

[Bitsyncmaster]

Thanks for all the suggestions.

I'm going to have him drive down to my house. I will pull his FD and check and clean the plunger. I will do some other testing also if I don't think the plunger is sticky.

[David T]

Thanks for all the suggestions.

I'm going to have him drive down to my house. I will pull his FD and check and clean the plunger. I will do some other testing also if I don't think the plunger is sticky.

During warm-up the CPR aka Warm-Up Regulator is controlling the fuel to a large extent. Also the WUR is supposed to give added enrichment following a fast throttle opening, kind of like an accelerator pump. I really doubt the fuel plunger is sticking only when cold. Make sure the vacuum hoses are hooked up correctly and the small, round delay valve is oriented correctly to the WUR. As long as you are checking things make sure the vacuum hoses are OK for the vacuum solenoid on the distributor. I would concentrate on the WUR and it's associated connections since you say you replaced it and you are still having trouble.

[hmcelraft]

37178

Probably vacuum related to WUR and delay valve. Be sure it is not on backwards. Be sure the delay of the valve is correct.

[sdg3205]

Run a 20oz bottle of Techron through it and see what happens before u dig in too deep. That stuff does amazing things.

Is the car new to him? Or is the problem new?

[Bitsyncmaster]

Run a 20oz bottle of Techron through it and see what happens before u dig in too deep. That stuff does amazing things.

Is the car new to him? Or is the problem new?

He has had the car for 15 years. He said it has had cold running problems since 2008 but has been getting worse from then.

[Bitsyncmaster]

37178

Probably vacuum related to WUR and delay valve. Be sure it is not on backwards. Be sure the delay of the valve is correct.

I had him check that and it seemed good from what results he reported.

[Bitsyncmaster]

Here is another video with the air cleaner off so I could see the reaction of the air plate to the throttle. Note the backfire sometimes. It that a clue. It also looks like the delay is less with this cold run and the air cleaner removed.

https://www.youtube.com/watch?v=PnzZhvG6UVs&feature=youtu.be

[DMC5180]

The backfire tells me it's running lean momentarily. Perhaps this is the point in diagnosing that a fuel pressure gauge should be installed for observation. Of coarse the downside is that you have to let the engine cool overnight to get a good observation.


Dennis

[DMCVegas]

Pull those injectors one at a time, and start checking spray patterns.

[DMC5180]

Pull those injectors one at a time, and start checking spray patterns.

That's a good suggestion.


Dennis

[DMCMW Dave]

That's a good suggestion.


Dennis

No, pull them all at once and check spray patterns. They all spray at the same time, and if you do it one a time you are filling the other cylinders full of gasoline.

[DMCVegas]

No, pull them all at once and check spray patterns. They all spray at the same time, and if you do it one a time you are filling the other cylinders full of gasoline.

Better idea indeed. If you're going to use the onboard fuel pump instead of a Injector Tester on a bench.

It might also be quite helpful as well to first pull those spark plugs, and see if one in particular has been fowled. That would be the first clue as to where you should focus.

From there you should check both the injector, as well as the spark plug wire.

[Ron]

It also looks like the delay is less with this cold run and the air cleaner removed.

https://www.youtube.com/watch?v=PnzZhvG6UVs&feature=youtu.be May sound backwards, but, is the port on the oil fill cap (to breather) blocked off during the vid? (too dark for me to see here).

[David T]

May sound backwards, but, is the port on the oil fill cap (to breather) blocked off during the vid? (too dark for me to see here).

If the motor runs OK when warm you may have a problem with the injectors but that is not what is causing the delayed response when cold. That is caused by something having to do with the CPR and/or the vacuum advance. Touching the injectors is just diverting your attention from the real problem.

[hmcelraft]

You can mess all you want - there is something wrong with the delay valve or the vacuum attached there to. No cold engine fuel enrichment are the symptoms. I don't think you have investigated that closely enough.

[DMCVegas]

Whoah, whoah, whoah!

https://don1uexbbetbo.cloudfront.net/content/art/features/wf_manage_stress_lg.jpg

This right here is a perfect example of what goes wrong with Shadetree Repairs, or even inexperienced professional mechanics. None of us are there for in-person troubleshooting, and we're trying to add our own opinions. Troubleshooting gets shot all to hell, or even ignored. Then we start chasing things around. God forbid the next thing is that this owner just starts throwing parts at this and runs up an expensive, and very unnecessarily expensive repair bill.

I've said what I've said based off my own experience with this very same thing. What you choose to do with that is up to you. And again, the exact same can be said for everyone else who keeps insisting upon taking you in a different direction. So, what to do?

Get. Back. To. Basics!

You can call a vendor, you can post online. But chances are that if you just follow your workshop manual and set the engine back to specification, that's going to take care of everything. But how to do that, and what to focus on? Well, here is your checklist:


GET THE FACTS! Start with how long this has been going on, and if it has been getting progressively worse.
WHEN DOES THIS PROBLEM HAPPEN? What are the specific conditions? Only when it's cold? Only when it's hot? Does it happen all of the time?
WHAT ARE ALL OF THE SYMPTOMS? What exactly is happening? Has there been a decrease in fuel economy? Have the emissions suddenly increased since then?
WHAT HAS BEEN DONE TO TRY AND "FIX" THIS, IF ANYTHING? Is there anything else going on that might have occurred that could potentially interfere with your troubleshooting or repair that also needs to be "undone" before achieving a successful repair?
IS THE ENGINE WITHIN OPERATING SPECIFICATIONS? Are all of the related components properly functioning within factory specific specifications? What isn't?



Now rather than tell you the shortcut as to what to do to fix this is, I'm going to tell you what I would do, and in what order to try and pinpoint this issue. Aside from "Getting Back to Basics", I use a method called "Divide and Conquer".

1. What is the problem? You've got a stumbling issue when cold. We have established that, and that it has been getting steadily worse since 2008. Great.
2. What does that narrow things down to? Well, we know that it is only when cold. That is the first thing. The second thing is that the LAMBDA system is radically cycling, and we know that occurs whenever there is a mixture issue. Chances are it's not a simple vacuum leak because it goes away when warm. Or at least probably mostly goes away as far as this owner's perception is.
3. What do we know the real, actual problem is? You are having a combustion issue. This may be occurring within a single cylinder, or it could be many. We don't know just yet, do we? We also don't know what exactly is causing the combustion problem. Is it a mixture problem, or an ignition problem? What do we do next?
4. Is the engine operating within proper specification? In order to operate properly, we know that we need to have good ignition wires, and no vacuum leaks. A quick inspection should take care of this. And if need be, there are other in-depth procedures to go through. Checking that wires and hoses are all in good condition and properly connected is the first step. And maybe that even resolves the issue. But if not...
5. How do we know if this is a system wide combustion issue across all 6 Cylinders, or if it is a single one? You need to remove and inspect each individual Spark Plug. Check them all for fowling, and most importantly you need to check and see if one particular one looks worse than the other.

If all of the Spark Plugs look the same:
Chances are you've got a system-wide Fuel Enrichment problem. At this point you need to test Fuel Pressures to verify that the Control Pressure Regulator is properly functioning. That goes for either an internal failure with the unit, or the vacuum system that controls it. AKA the Warm Up Regulator, that isn't a totally proper description since it also enriches the mixture on a warmed-up engine during RPM spikes.


If one (or more) Spark Plug(s) looks worse than the rest:
Then you know that you've got a combustion problem that is isolated to that particular cylinder. The air/fuel mixture isn't catching fire properly. So you've either got an issue with improper ignition that doesn't deliver a hot enough spark to catch the mixture on fire. Or... You've got a problem with the fuel not properly atomizing, so that it cannot catch fire. So then you've got to check either the wire for arcing sparks that are sapping it's power, or the spray pattern of of that particular injector or injectors to see if they are clogged.


And even then, this is just for starters. From there you have got to continue on, and it may be either something else entirely, or there may be more than one problem here going on. Or hey, you might just quickly find the culprit and get the problem fixed in no time! But at this point you need to exonerate your existing components from problems. Otherwise, you're just pointlessly chasing ghosts, and wasting both time and money in the process. Do this first before anything else. If need be, contact a vendor directly.

[Jonathan]

Run a 20oz bottle of Techron through it and see what happens before u dig in too deep. That stuff does amazing things.

I'm almost halfway through a tank of gas with this in it. Well, the STP fuel injector cleaner version available at the local Crappy Tire. Will let you know if/what I notice once it's gone through the system completely.

I don't know if everything written in this thread applies to my car, but "delayed throttle" in some ways would describe the first few blocks of taking my car out for a spin lately. It tends to go away by the time I leave my subdivision and doesn't happen again until the next day.

[Ron]

...since it also enriches the mixture on a warmed-up engine during RPM spikes.Oops...
"Above 40 C, the acceleration enrichment circuit is inoperative."

========

If you look at the plunger, check out the roller it rides on while you are in there. (seized/flat spot/...).

[DMC5180]

Oops...
"Above 40 C, the acceleration enrichment circuit is inoperative."

========

If you look at the plunger, check out the roller it rides on while you are in there. (seized/flat spot/...).

What IF the thermal vacuum control valve was bad (stuck in the closed position) since 2008 or someone connected the hoses in the wrong orientation.

You would never see vacuum to supply the enrichment circuit.

Once the engine has warmed above the threshold where enrichment was needed it would run normal.

It seems like that valve has a low failure rate but it is possible.

[DMCVegas]

Oops...
"Above 40 C, the acceleration enrichment circuit is inoperative."

Then you know what? My mistake. I must have been thinking of another CIS application where the vacuum feed to the CPR is NOT affected by engine temperature. Such as the 5 port configurations.

That still does not change the fact that a methodical testing procedure NEEDS be initiated here rather than simply chasing ideas. That leads to twisting and omitting facts in order to suit theories, rather than the other way around so that the truth can be found. And it just seems like in the quest to be the person with the right answer, it has become a competition here to the point where we just want to discount everyone else's input thinking that if only our own is left it will somehow magically become the correct diagnosis by default. It is indeed one of the largest pitfalls of the DIY'er to when asking for help on an amateur forum.

There are a thousand "what if's" here. What this car needs are facts instead in order to properly formulate an accurate diagnosis. That is what needs to be focused on.

[Bitsyncmaster]

Great thinking guys. I think I do need an approach list to finding this problem since it only shows up for a cold engine.

So when the owner gets to my house:

1) Park outside, open engine cover, remove spark plugs to determine if one cylinder may be causing the problem.
2) Pull injectors (all six) and put in bottles. Jump RPM relay and do a spray test. Good time to replace injector seals.

I do have a vacuum source and gauge, so maybe I can do some testing of thermal switch if engine has cooled off by then.

3) Set up my fuel pressure tester. Test primary pressure jumping RPM relay. This makes me think, can I test control pressure (open the tester valve) without starting the engine?

So I will have my fuel pressure tester set to read control pressure and vacuum gauge hooked up to the WUR port when we are ready to start the cooled off engine.

Start engine and I will have a list to record control pressure and vacuum. as engine warms up.

[Bitsyncmaster]

I forgot to mention this owners car also has the wideband setup that I have. So it only takes about 20 seconds for the lambda system to got closed loop after a cold start.

So since it's cold this morning (45 deg. F), I opened my cars engine cover and the garage to let it cool down so I can do a punch throttle test on a cold engine later this morning.

[Bitsyncmaster]

Here is a video of my DeLorean cold start.

https://youtu.be/U5jR4KCCbE8

My car had not been started for a few weeks. Garage was open for a few hours with outside air temp at 45 deg. F.

I did get a couple backfires punching the throttle. I never punch the throttle so quickly so never knew it would back fire. Not really concerned with that condition.

Sounds like I need a valve adjustment since I hear it ticking running that cold.

[David T]

Here is a video of my DeLorean cold start.

https://youtu.be/U5jR4KCCbE8

My car had not been started for a few weeks. Garage was open for a few hours with outside air temp at 45 deg. F.

I did get a couple backfires punching the throttle. I never punch the throttle so quickly so never knew it would back fire. Not really concerned with that condition.

Sounds like I need a valve adjustment since I hear it ticking running that cold.

The CPR won't make a cold engine run like a warm engine. Till it warms up it will stumble a little and not run as smooth. Before getting out all of the test equipment the best tester you have is your 2 eyes. Examine all of the vacuum hoses by the CPR and the vacuum advance. Make sure the vent hose on the CPR is not kinked or plugged up. Since we have seen these symptoms before we can narrow down the initial problem area to the systems that are active during warm-up. Till they are proven good it is best to confine the testing to ONLY that. Otherwise you will go off on tangents and disturb other things that may not need to be messed with and may introduce other problems.

[Jonathan]

Here is a video of my DeLorean cold start.

https://youtu.be/U5jR4KCCbE8

My car had not been started for a few weeks. Garage was open for a few hours with outside air temp at 45 deg. F.

I did get a couple backfires punching the throttle. I never punch the throttle so quickly so never knew it would back fire. Not really concerned with that condition.

Sounds like I need a valve adjustment since I hear it ticking running that cold.

Hey Dave, this could find its way into another thread it if gets us too far off track, but after seeing you not have an idle microswitch in place where it normally would be, what all modifications do you have to your car that aren't as originally designed or stock?

Robert made a good point about the time-out or going about troubleshooting in a methodical way and knowing what you are dealing with, and part of that would be knowing not only the condition of the car, but also what changes are in the car that are different from the factory.

I realize the original intent of the thread was on a friend's car, so how yours behaves is a separate issue, it just made me think about how sometimes we skip over differences and that piece of information could be key in figuring out a problem on a car.

I know when I see a thread asking for help on a carbed or EFI car, I generally keep quiet if it's in an area I know differs from stock (due to my lack of knowledge on those set-ups). Not just engine swap differences, but the upgrade modules you sell and other things (like understanding why there isn't an idle microswitch on your car) can get a lot of guesses going in directions they didn't need to go.

Just a thought anyway. I think I'll put together a list of what isn't factory on my car, plus things that are upgraded or have had recalls done, just to remind myself/others what the starting point is. Might put it in my forum signature depending on how long it is.

[Bitsyncmaster]

As stated, both cars have wideband. That results in closed loop lambda in 20 seconds of running. Since both cars have the stock WUR which make the mixture richer when cold, the lambda would be trying to lean the mixture to 14.7 AFR. Now weather the lambda can overcome that very rich mixture when cold, I have not tested. Both of us have cut the thermister/WOT switch wire that was going into the lambda ECU

Both of us also have my RPM relay.

My car has the hot start relay running without the thermotime switch connected.

My car also has my idle ECU and right now I have no deceleration valves.

Of course I have all solid state relays but those should not affect these tests. My primary pressure is shimmed to 75-76 PSI. Hot mixture is set to stock dwell values. I don't have the idle switch so advance goes on above 1500 RPM. The stock unit would hit advance a little sooner. I have no WOT switch since I have a console switch for selecting a richer mixture (think it's set to 13.2 AFR). My video test was done with lambda set to 14.7 AFR.

There is no vacuum advance on a cold engine anyway.

I wonder how a stock setup would work punching the throttle on a cold engine (air cleaner removed). Anybody care to try?

[Ron]

Dennis,
We're usually on the same page, but I'm not even following your response(s):


What IF the thermal vacuum control valve was bad (stuck in the closed position) since 2008 or someone connected the hoses in the wrong orientation.

You would never see vacuum to supply the enrichment circuit. I agree, being why I said "Thermal Vacuum Switch (hung at warm position/not getting supply/etc)" in my first post (#4)??


Once the engine has warmed above the threshold where enrichment was needed it would run normal.I agree. But it does??
The OP says, "My friends DeLorean has a cold engine delayed throttle response. When the engine has warmed up the problem goes away." To me it had Cold Acceleration Circuit written all over it...resulting in my 1st post in general, which seems obvious even when I re-read it, so I at a loss here?? The last thing I want to do is confuse someone (where I'm at now ;-)


It seems like that valve has a low failure rate but it is possible.
Agreed. But, fwiw, I had to call Julee and order one for mine last month (both ports passing ), Chuck's and Jim's earlier (stuck in COLD position).

Maybe this will help - My only purpose in the post you quoted was to quote the manual to correct a misstatement related to the problem....:hmm:

[DMC5180]

Ron,

Sorry, I missed seeing your # 4 post.

I realized you were just correcting the previous line quote. I went back to the manual to verify how the vacuum switch functioned before making my previous post.

And then there is this auto correct feature on my phone that changes words after typing something that I fail to catch with a quick scan proof read.

Sometimes my thoughts are a bit disconnected. I'm get old [emoji12]

[Ron]

No problem bud! It seems I got under Robert's skin somehow with the same post. ..and Rob's the other day???
Yeah, I can relate -- I've done been old. To old for this $hit!:tongue:

[Ron]

Then you know what? My mistake. I must have been thinking of another CIS application where the vacuum feed to the CPR is NOT affected by engine temperature. Such as the 5 port configurations.Um,...five lashes with a wet noodle!?!
Mine has 5 ports, but only 2 have vacuum feeds. (That's one on me, since I have seen some with less, but not more ;-)


That still does not change the fact that a methodical testing procedure NEEDS be initiated here rather than simply chasing ideas. That leads to twisting and omitting facts in order to suit theories, rather than the other way around so that the truth can be found. And it just seems like in the quest to be the person with the right answer, it has become a competition here to the point where we just want to discount everyone else's input thinking that if only our own is left it will somehow magically become the correct diagnosis by default. It is indeed one of the largest pitfalls of the DIY'er to when asking for help on an amateur forum.

There are a thousand "what if's" here. What this car needs are facts instead in order to properly formulate an accurate diagnosis. That is what needs to be focused on.No need to convince me. I've been with you on the basics and methodical testing. First post I mentioned the basics, first. And since the cold acceleration enrichment circuit is written all over the OP (going lean, cold), the components/ect the circuit relies on, and vacuum leak(s) that are usually noticeable only when cold. Seems reasonable, if not most likely, right or wrong, imho.
As for the post quoted, as I said above, its only purpose was to quote the manual to correct a misstatement related to the problem....and a suggestion IF he checked the plunger (a good idea imo).

In other words, quit picking on me...at least when we agree :deviltail:

[David T]

I am guessing but the accumulated result of all of the mods makes the motor run leaner when cold. That would negate some of the effect of the CPR trying to run the motor with a richer mixture when cold. That's why you see the pronounced and exaggerated throttle delay effect. Going into closed loop so quickly on a cold O2 sensor is not a good idea, at least put a heated one in so it can warm up fast.

[DMCVegas]

Um,...five lashes with a wet noodle!?!
Mine has 5 ports, but only 2 have vacuum feeds. (That's one on me, since I have seen some with less, but not more ;-)

No need to convince me. I've been with you on the basics and methodical testing. First post I mentioned the basics, first. And since the cold acceleration enrichment circuit is written all over the OP (going lean, cold), the components/ect the circuit relies on, and vacuum leak(s) that are usually noticeable only when cold. Seems reasonable, if not most likely, right or wrong, imho.
As for the post quoted, as I said above, its only purpose was to quote the manual to correct a misstatement related to the problem....and a suggestion IF he checked the plunger (a good idea imo).

In other words, quit picking on me...at least when we agree :deviltail:

Whenever I see a K-Jet thread, "The End" starts playing in my head, and I just have a thousand yard stare as I type.

37252

Flashbacks of arguments over troubleshooting methods, among other things... I tend to loose my sense of humor, and go into that defense mode because usually at that point everything is an attack rather than an actual discussion. My bad, and I do apologize.

Now I can get back to normal!

37253



I am guessing but the accumulated result of all of the mods makes the motor run leaner when cold. That would negate some of the effect of the CPR trying to run the motor with a richer mixture when cold. That's why you see the pronounced and exaggerated throttle delay effect. Going into closed loop so quickly on a cold O2 sensor is not a good idea, at least put a heated one in so it can warm up fast.

The best advice that I ever got about car repair was from my own DeLorean mechanic that I used to balance my CO and replace my clutch. I asked him how he was able to know just what to do for the wide number of cars that he had to get them all fixed so quickly. He just pointed to the library of service manuals that he had in his office, and told me that there is no secret to repairing cars. It's just a matter of getting them back to spec. Even when you tune cars for track or anything else, you still just need to get them into spec for that particular application. It's not an art form or a unique talent in the least to read a manufacturer's guide, and then set everything back to the manufacturer's specifications with some gauges and an exhaust gas analyzer. The biggest thing is just understanding what you're reading.

If you're gonna disable or modify the LAMBDA system, you've got to modify the K-Jetronic system to go back to a fully independent operation without it. Otherwise, return it back to fully functioning operation, and then set all other components back to spec. LAMBDA understands that engines get cold. That is why it has it's own temperature probe to know when the engine is cold, so that it can work in cohesion with the Control Pressure Regulator for a properly enriched fuel mixture. There are two completely separate Cold Operation Circuits at play here. Both Mechanical and Electronic. They are designed to work in tandem with one another, and as such compensate for the operations of each other in their measurements of fuel flow.

I don't know what the reasoning was behind the modifying the LAMBDA circuit at all. If you do not have deceleration valves, you NEED to modify your ISM Microswitch to engage quicker to gently decelerate RPMs. Otherwise that also forces a temporary choke condition that spikes fuel mixtures and plays hell with the fuel system as well as the emissions. So you potentially have THAT going on as well.

At this point, there are so many other mods going on here, and now a second car involved, that I just don't know what to tell you other than to get the thing back to stock, and all will be fine.

[Ron]

Now I can get back to normal!

37253
37257

==========

Kjet diagnostic threads w/o a gauge involved usually get my vote...

[hmcelraft]

Dave M

Cold engine - quick throttle with air cleaner off - no hesitation (all stock - Approx 15,000 miles on fresh tune).

3354 - Automatic

[Bitsyncmaster]

Dave M

Cold engine - quick throttle with air cleaner off - no hesitation (all stock - Approx 15,000 miles on fresh tune).

3354 - Automatic

Thanks for that test. I think that backfire my friend was getting (I also got a few) is probably due to us running closed loop lambda to soon before the engine warms up. My friends car has the hesitation (delayed throttle) and mine does not.

So my plan to solve his issue is to adjust his idle screws (curb idle, idle switch) to bring his idle back down to closed loop 775 RPM. Then adjust his mixture (dwell) to stock. He has been playing with those adjustments.

Then we are going to pull the spark plugs and examine and replace with new. This will tell us if one or more cylinders is not equal.

Will then pull the six injectors and do a flow test and spay test into six jars. We will also install new injector seals when we put them back in.

Will then primary pressure test. Hopefully by then the engine has cooled and we can start the engine and read control pressure as it warms.

[FABombjoy]

I think that backfire my friend was getting (I also got a few) is probably due to us running closed loop lambda to soon before the engine warms up.
Afterfire, technically :D

I have an LC-1 and get this too. I bypassed the thermostatic valve but even with cold vac advance it still happens a little.

[DMCVegas]

Thanks for that test. I think that backfire my friend was getting (I also got a few) is probably due to us running closed loop lambda to soon before the engine warms up. My friends car has the hesitation (delayed throttle) and mine does not.

So my plan to solve his issue is to adjust his idle screws (curb idle, idle switch) to bring his idle back down to closed loop 775 RPM. Then adjust his mixture (dwell) to stock. He has been playing with those adjustments.

Then we are going to pull the spark plugs and examine and replace with new. This will tell us if one or more cylinders is not equal.

Will then pull the six injectors and do a flow test and spay test into six jars. We will also install new injector seals when we put them back in.

Will then primary pressure test. Hopefully by then the engine has cooled and we can start the engine and read control pressure as it warms.

Sounds good. When you start playing with adjustments, you see all kinds of weird things...

When cold though, I believe the idle should be around 1,200± RPMs though if I'm not mistaken (don't have my manual, someone needs to verify that number). Warms the engine up quicker to reduce emissions and fuel consumption, and heats the LAMBDA probe for immediate operation and fine tuning.

[DMC5180]

Sounds good. When you start playing with adjustments, you see all kinds of weird things...

When cold though, I believe the idle should be around 1,200± RPMs though if I'm not mistaken (don't have my manual, someone needs to verify that number). Warms the engine up quicker to reduce emissions and fuel consumption, and heats the LAMBDA probe for immediate operation and fine tuning.

I don't believe the idle ECU has a two step setting. It's just 775 all the time when everything is functioning as it should.

Other Volvo ECU's do have an idle increase feature for A/C cycling.

Modern day EFI does have a map that increases rpm on cold engine though.

[DMCVegas]

I don't believe the idle ECU has a two step setting. It's just 775 all the time when everything is functioning as it should.

Other Volvo ECU's do have an idle increase feature for A/C cycling.

Modern day EFI does have a map that increases rpm on cold engine though.

Nope. Part # 102480

The Idle Speed ECU has it's set map to achieve 775± RPMs when warm. However, the Idle Speed Thermister sits inside of the Coolant Y-Pipe on top of the engine to detect when the engine is cold or not. When it's cold and that switch is triggered, the ECU internally shunts over to the 1,200± RPM range. It helps to get cold engines going, and of course warm the engine up to decrease emissions as soon as possible. Plus without a heater wire, it extends the life of the O2 sensor for fine-tuning of emissions. Save for the heater wire portion (modern EFI has that function to get the O2 sensors online as quickly as possible), ALL engines run faster when cold.

If you're not increasing RPMs when cold, that is something you should definitely check out. K-Jetronic has evolved over the years, and the additional systems were all meant to work in tandem as they were intergrated in. So if it's not up to the proper speed, you might just see some other odd behaviors.

Now older 2.7L PRVs on Volvos were a different animal from what I beleive. And please, feel free to correct me if I'm wrong here. But the older K-Jetronic systems had a balancing tube aft of the throttle plates, and you used the 3 brass screws to set the idle and balance the mixtures between cylinder banks. Volvo/BOSCH then installed what was called an "Auxillary Air Valve" that was mechanical in function. When it was cold, a bi-metal arm would slide the valve up to increase cold engine RPMs, and as it warmed it would close back. And THEN perhaps if you had an A/C system, the AAV would pop back open. Kind of like how carburetors would have the kicker solenoid for the same reason. When you have a physically set Idle Speed set by screws, the system cannot compensate for additional loads at Idle, no.

However, when you have a variable Idle Speed Controller, such as we do with the Idle Speed Motor and modern EFI cars (WITHOUT "Drive By Wire" technology) have to separately meter air, there need not be an A/C switch involved at all. When the A/C kicks on, the load decreases the RPMs. The Idle Speed ECU detects this, and opens the rotary valve more. When the A/C cycles off, the cycle goes in reverse. With this system, we don't touch a thing. Close off the Idle Screws, and let the ECU do all of the work. Far less complicated, and easier to tune.

[DMC5180]

Fair enough.

Foggy memory on my part, I've been using Dave M's digital ECU for several years now. I just don't recall the old ECU doing the raised idle when cold. (Unless the micro switch wasn't tripped do to worn linkage)

[Bitsyncmaster]

When I was running the stock idle ECU, it would only have a higher RPM than 775 for a few seconds after a cold start. Now I don't remember running the engine much below 30 deg. F so maybe it would fast idle below that temp.

[David T]

When I was running the stock idle ECU, it would only have a higher RPM than 775 for a few seconds after a cold start. Now I don't remember running the engine much below 30 deg. F so maybe it would fast idle below that temp.

Maybe everyone should refresh their memory and refer to D:05:01-:04. Below 59 degrees F it says it goes to a fast idle but it doesn't specify an actual speed. In the notes it says the idle is calibrated to 775 RPM's + - 50 RPM (above 59 degrees F coolant temp).

[Ron]

When I was running the stock idle ECU, it would only have a higher RPM than 775 for a few seconds after a cold start. Now I don't remember running the engine much below 30 deg. F so maybe it would fast idle below that temp.Yeah, the coolant gets above 59F pretty quick...but kjet don't need fast idle as much as a carb (consider there is no separate enrichment device for warm acceleration like a spray pump...) .

Dave, you never said if you/friend was plugging the oil fill port to breather during the vid(s)??

[Bitsyncmaster]

Dave, you never said if you/friend was plugging the oil fill port to breather during the vid(s)??

No we did not plug the oil fill port breather. Never thought that would make any difference since it's just open into the air cleaner.

[Bitsyncmaster]

Maybe everyone should refresh their memory and refer to D:05:01-:04. Below 59 degrees F it says it goes to a fast idle but it doesn't specify an actual speed. In the notes it says the idle is calibrated to 775 RPM's + - 50 RPM (above 59 degrees F coolant temp).

Maybe my stock ECU was bad or that document is incorrect (have we ever seen documents wrong?).

So what do other owners see when starting below 59 deg.?

[DMC5180]

Maybe everyone should refresh their memory and refer to D:05:01-:04. Below 59 degrees F it says it goes to a fast idle but it doesn't specify an actual speed. In the notes it says the idle is calibrated to 775 RPM's + - 50 RPM (above 59 degrees F coolant temp).

Good point David.

In my mind I was thinking the thermistor op temp was below 115 F. I confused it with the Vacuum control switch. Funny thing is, I had been looking at that page in the manual a couple days ago and even saw the below 59 F. It just didn't sink in at the time because I was focused on Vacuum control temp. Either way it's not to often that I fire up the D with temps in the 50's. That would likely be the main reason I couldn't recall it doing the warm up idle back when I had a stock ECU.

[Bitsyncmaster]

Good point David.

In my mind I was thinking the thermistor op temp was below 115 F. I confused it with the Vacuum control switch. Funny thing is, I had been looking at that page in the manual a couple days ago and even saw the below 59 F. It just didn't sink in at the time because I was focused on Vacuum control temp. Either way it's not to often that I fire up the D with temps in the 50's. That would likely be the main reason I couldn't recall it doing the warm up idle back when I had a stock ECU.

The idle thermistor is not a one point setting (a switch). It is a variable resistance that is about 100 Kohms very cold and 1 Kohm when hot. Wasn't the throttle enrichment switch set for 59 deg. F.?

[DMC5180]

The idle thermistor is not a one point setting (a switch). It is a variable resistance that is about 100 Kohms very cold and 1 Kohm when hot. Wasn't the throttle enrichment switch set for 59 deg. F.?

Good point again. The Device in the RH leg of the y- pipe. Is it a Switch or thermistor ?

[Bitsyncmaster]

Good point again. The Device in the RH leg of the y- pipe. Is it a Switch or thermistor ?

I'm pretty sure the idle speed thermistor is in the Y pipe. I think the thermal throttle enrichment switch is also in the Y pipe. I seem to remember three things in the Y pipe so the vacuum switch is the other.

[DMCVegas]

I'm pretty sure the idle speed thermistor is in the Y pipe. I think the thermal throttle enrichment switch is also in the Y pipe. I seem to remember three things in the Y pipe so the vacuum switch is the other.

These are the items screwed into the Y-Pipe.


Thermistor Switch for the Idle Speed ECU.
LAMBDA Switch for the LAMBDA ECU.
Vacuum Switch for the CPR & Ignition Distributor.


The Thermotime Switch that fires the Cold Start Valve is located below the Thermostat in the Water Pump, and the Temperature Switch for the Temp Gauge in the Binnacle should be at the end of the right cylinder head if memory serves.

[Ron]

No we did not plug the oil fill port breather. Never thought that would make any difference since it's just open into the air cleaner.
No, that is a vacuum leak -- Feel it.
(The crankcase is under vacuum, as is the breather for that matter... ;-)


Maybe my stock ECU was bad or that document is incorrect (have we ever seen documents wrong?).

So what do other owners see when starting below 59 deg.?I get:
~925 RPM.
~29 psi Control Pressure
~55° Dwell (steady)

As it warms:
~760 RPM (gradual drop)
~50 psi Control Pressure (within 1/2 min or faster [I don't like this, but...])
~40° Dwell (pulsing)

RE cold throttle snap test requested:
Ambient 74F, cold engine running ~10 seconds..
Revved without any problem (but not at all as strong as when warm ;-).

[Bitsyncmaster]

No, that is a vacuum leak -- Feel it.
(The crankcase is under vacuum, as is the breather for that matter... ;-)

I get:
~925 RPM.
~29 psi Control Pressure
~55° Dwell (steady)

As it warms:
~760 RPM (gradual drop)
~50 psi Control Pressure (within 1/2 min or faster [I don't like this, but...])
~40° Dwell (pulsing)

RE cold throttle snap test requested:
Ambient 74F, cold engine running ~10 seconds..
Revved without any problem (but not at all as strong as when warm ;-).

Thanks for the testing. So I guess my stock idle controller was bad. So it took about 2 minuets for the idle to drop to normal RPM? What was the ambient air temp when you had the fast idle?

[DMCVegas]

I get:
~925 RPM.
~29 psi Control Pressure
~55° Dwell (steady)
.

Hmm... When my Idle Speed Circuit was bad, I had swapped out the Idle Speed ECU with one I bought off eBay. It turns out that it was a bad harness, so I grafted in a new wire to the ISM and it ran fine after that, but I never bothered to swap the OEM unit back into place since everything was running fine. That was during the first winter that I owned my car, and the cold idle was around 1,200 RPMs.

Hell, I'm wondering now if I got lied to about the origins of that ECU, and if I might just have the wrong module in there from another damn car...

[Ron]

So it took about 2 minuets for the idle to drop to normal RPM? What was the ambient air temp when you had the fast idle?



Hell, I'm wondering now if I got lied to about the origins of that ECU, and if I might just have the wrong module in there from another damn car...No, more like a minute, if that, but it was parked inside my shop all night (69F) and I opened the doors where it was much warmer and immediately started it, fwiw. (My CP comes up fast imo, as noted above ;-)
Oops, I meant to include the ambient temp for those tests too. It was 69F.

It's supposed to be ~46F in the AM. I'll do the snap test again, get the cold RPM...time to 760, and CP (since I left the gauge hooked up ;-).

[Bitsyncmaster]

No, more like a minute, if that, but it was parked inside my shop all night (69F) and I opened the doors where it was much warmer and immediately started it, fwiw. (My CP comes up fast imo, as noted above ;-)
Oops, I meant to include the ambient temp for those tests too. It was 69F.

It's supposed to be ~46F in the AM. I'll do the snap test again, get the cold RPM...time to 760, and CP (since I left the gauge hooked up ;-).

So your engine was probably above the book value of 59 deg. F. I wonder why you even got a fast idle.

[Ron]

Good question. I don't know...maybe thermister is off a little (59 +/- 3, so 69 - 62 = 7° off of the shop thermostat??). Not sure if the WUR/CPR pressure being down until ~104F (rich) would affect it...have to think about that one ;-)
If Robert's is correct at 1200 RPM with lower temps, I'm happy. lol

I was up very late on a call last night so I'll have to do the other tests in the AM...

[DMCVegas]

My temperatures I know were in the low 40's when I was dealing with this. Enough to still generate a few whiffs of steam in the winter. Since it is a Thermister with variable outputs and not a simple on/off switch, and the manual refuses to specify what the specific over/under of the cold RPMs are, maybe the cold idle speeds are variable then. After that I just know that I never paid attention to start up RPMs again. I'd just get in, close the door, fasten seatbelt, crank the engine, and in the time it takes to get my phone plugged in and charging and my radio set to whatever music I wanted to hear, I just used that as the quick warm-up period for the engine. Then I just hit the gas and took off.

[Bitsyncmaster]

Good question. I don't know...maybe thermister is off a little (59 +/- 3, so 69 - 62 = 7° off of the shop thermostat??). Not sure if the WUR/CPR pressure being down until ~104F (rich) would affect it...have to think about that one ;-)
If Robert's is correct at 1200 RPM with lower temps, I'm happy. lol

I was up very late on a call last night so I'll have to do the other tests in the AM...

I would guess you were still closed loop idle even with the rich mixture. Yes a rich mixture increases idle speed but the cold oil should should compensate for that.

I think we need to get a few other owners to do the test when they know the temp is very cold.

[Bitsyncmaster]

My friend came over today for some more help with his problem.

First thing I did was check what he had adjusted the mixture to. It was not to far off, just a little on the rich side. I then backed off his curb idle screw a little to bring the idle down to 775 RPM.

Then we pulled all 6 injectors and did a flow test. Results were very bad as shown on the attached photo. Now come to find out, his FD is one of the adjustable units. First we swapped the injector lines on the worst and best flows. The low flow did not follow the injector so it must be the FD causing the problem.

Well I did many adjustments and nothing seemed to fix the flow rates. It even seemed to get worse and I could see that low flow injector was cutting on and off. But as it turned out, my first flow test I must have not pressed the air plate fully down all the way and subsequent tests I did press it all the way down. So ready to give up I thought maybe we should test the flow with it pressed less then half way down. Bingo, now 4 of the injectors were nearly equal the two were maybe 75% or the other four.

So anyway, we did not try adjusting with the air plate less pressed. I think something is bad with the FD because of the major problem with it fully depressed. His adjustable FD is a 0438-100-109. Where as my adjustable FD is a 0438-100-079.

If it was me, I would try to rebuild the FD but he is not willing to attempt that. He will see if anything changed with our adjusting and the new injector seals we installed.

[DMCVegas]

My first concern here is that he doesn't have the properly calibrated Fuel Distributor for the PRV application. I say that because it's obviously not original, nor do we know if it's flow rates are within specification of the PRV's fuel delivery needs. But you can research that a bit to verify. Probably over on Pelican.

Now then, let's assume that this Fuel Distributor is totally compatible with the PRV here. The next steps that you need to take is to calibrate that whole entire set up. And you're gonna need to do that in 4 parts.

Phase 1:
You need to get the fuel injection components cleaned. *Technically* you really should remove the system and bench repair and test. BUT if you insist upon the least invasive, and most time consuming procedure, ONLY USE TECHRON to clean things out. Otherwise, you really gotta pull it to clean it.

Phase 2:
Remove all of the injectors from the engine. Using an Injector Tester with a 100 PSI gauge, you not only need to inspect for proper spray patterns, you absolutely need to verify that each injector cracks at the same PSI. If one of them is way off or leaks prematurely, you need to try and clean it. If that doesn't work, you've got to replace it. (Note: it leaks under low pressure, you're gonna have a damn Hot Start issue, so replace that injector)

Phase 3:
ONLY APPLICABLE BECAUSE OF NON-DELOREAN PARTS!
Normally this is conducted on a bench, but you *can* do it on the engine. What you need to do is reconnect all 6 Injectors back to the fuel Distributor, and place each one into an individual Graduated Cylinder. From there you've got to run the fuel pump and then press the plate in the Air Meter down about halfway. Do that for a few seconds, and then look at your results to see what your variations are.

Phase 4:
Balance the Air/Fuel Ratio.


If none of that works, it's time to suck it up and buy a whole new fuel distributor and potentially other parts because we don't know what is stock, and what is not. Plus if it's not stock, prepare to pay extra core charges for new parts.

[Bitsyncmaster]

I agree we don't know what the basic fuel flow should be. If we knew the correct values at a few points of the location of the air plate we could check for that flow rate. But there is some leeway there if you have the lambda system operating closed loop. It could adjust the basic flow rate to some degree. Actually if the dwell reads the same at those test rates it would say you have a very good FD. But that would require testing under load (on a dyno).

I do think there is something gone wrong with his FD since with the air plate fully depressed there is really bad flow results. I wonder if fully depressed it something that can never happen. Does anybody know? Do we also know the fuel flow (oz/min) at those locations?

When I did my FD adjustment I think I only used about half the distance pressing the air plate. Mine was very good and I tweaked one injector just a very little. That's why I like working on my own car. I can stop work and think about things to do. When working on someone else's car, they have to get it back on the road before the end of day.

Yes, injector testing is the best way to start.

[DMCVegas]

No, no. I think you misunderstood me about checking the flow rate. I'm not saying to ensure that the injectors discharge a specific amount of fluid within a certain period of time.

What I am saying is that if you hold down the metering plate for a specific period of time, do the injectors simply spray the same amount of fuel equally? Here, take a look at this video for a visual:


http://youtu.be/6yrwqspHhak

http://youtu.be/6yrwqspHhak

[David T]

No, no. I think you misunderstood me about checking the flow rate. I'm not saying to ensure that the injectors discharge a specific amount of fluid within a certain period of time.

What I am saying is that if you hold down the metering plate for a specific period of time, do the injectors simply spray the same amount of fuel equally? Here, take a look at this video for a visual:


http://youtu.be/6yrwqspHhak

http://youtu.be/6yrwqspHhak

The correct part # is 0438 100 109. If it isn't working send it out to be rebuilt. Send the injectors too and have them cleaned.

[Ron]

I am 99% sure I have the same adjustable FD. I will check after I run an errand.
Anyway, I would suggest following Robert's list but before putting the injectors back on that you perform the same steps without the them. I thought I posted my flow results here but can't find them (first sign, measured idle plate distance, 1/4,1/2, 3/4, fully depressed) I got just over ~6.4 oz per port per minute IIRC, and just a very little less with injectors installed fully depressed, but couldn't see any difference at other rates. I did have to adjust one port that was giving almost 7.0 initially (w/o injector, fully depressed). No idea if a PO had to set it up this way, but my spare stock FD gives the same results. I.E. It should work fine. I used 6 plastic baby bottles...they are graduated and fuel doesn't seem to bother them at all.
Just in case, what you can see now are caps, the adjustments are underneath...same tool as CO adjustment.

[Ron]

Something odd here- that number pops up as:
37700
4 cylinder cars ???

And, mine has a different number (0 438 100 109) which BOSCH shows to be correct.
37702
But the 0 438 100 109 in their illustration is adjustable ???
37701
:dunno:

Anyway, I found an old flow test that might help:
No injectors; fully depressed; 1 minute; 6.4 oz each port
No injectors;~1/2 depressed; 1 minute; 3.6 oz each port
W/ injectors; fully depressed; 1 minute; 6.2 oz each port (3 tests run, cold, CPR/WUR disconnected, Test valve shut- CP 55 psi, PP 72 psi)
(The 1/4 way depressed and ~.125" (whatever I measured previously at cold idle) was on the next (missing) page :-(

A previous test (with customer's stock FD and used injectors, 1/2" from fully depressed iirc):
5.75 6.40<= #1 (this port had a dimple in the FD diaphragm right under its valve.)
5.70 5.30
5.20 5.40
A spare plate brought them all to ~6.0 oz with cleaned injectors...

[Bitsyncmaster]

Thanks for the data you guys have posted.

I definitely got less flow from the FD when the plate was fully pressed than when pressed half way down. I used a digital scale and only got 2.72 oz. from the best one fully pressed for 40 seconds. That pretty much tells me the FD needs to be rebuilt. My friends car was a Houston bought car about 20 years ago so the FD change was done 20 or more years ago.

By the way, I checked how far the adjusters were set for on two of the "working" cylinders and it was 1.5 turns from fully closed.

I did check the primary pressure after finding the uneven flow rates and it was 70 PSI.

I just rechecked the part number on my FD and it is 0-438-100-076.

Now you have me thinking. Maybe I should have blocked the control pressure (hose to WUR) doing the flow testing. Do you think that would matter?

[Bitsyncmaster]

Still thinking about testing flow rates to get a standard chart.

1) Mixture has to be adjusted correctly before starting the test. That sets how far the FD plunger position is set.

2) Make up some test plates of a flat surface with a measured length rod in center so you can calibrate how far the air plate is pressed with the testing. You would use that plate pressing the plate down at the rear (back side of car) side to get repeatable results.

3) Measure and record the primary pressure. Not sure if that pressure would affect the results. Also would cap the control pressure (leave the gauge valve closed).

I may plan to do this testing on my car even though my car seems to run perfectly but I don't have the stock FD. I would do this testing next time I plan to go into the VOD since its some work to pull the six injectors. If you look at the air plate running the engine at high RPMs it really does not move down much more than a quarter inch. I would guess it moves more under load. It would be interesting to instrument it's movement during a dyno pull.

You could use graduated bottles or a weight scale to get accurate measurements of flow.

John's web site shows my "076" is for a Volvo and shows the "109" is for DeLorean. So why is this "109" and adjustable version?