Delayed throttle

[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=PnzZ...ature=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!



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:

1. GET THE FACTS! Start with how long this has been going on, and if it has been getting progressively worse.
2. 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?
3. 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?
4. 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?
5. 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.