running better before warming up

[Parzival]

When I start my car fresh on a day, the idle sits right where it should and acceleration is smooth. However when it reaches warm up temp the idle starts to hunt a bit, not a huge range stays between 750 and 900, and I get a little bit of jerking in acceleration intermittently.
I hear a lot of people say the opposite, telling me that the car runs a bit rough, but then is perfect when warmed up. I still have the tamper proof plug in my fuel air mixture adjustment, so its still set from the factory. I have new stainless fuel lines, and new spark plugs. Could this mean the air fuel mix needs adjustment? or is there something else at play?

[Jonathan]

I would bet it's your idle microswitch not staying fully engaged once the engine is warm. Likely from a slightly weak or sticky return spring that's not quite strong enough to pull it back against the vacuum produced by a hot engine. You can try one of two things (or both): spray some lube in on the spring that sits at the pivot point of the idle microswitch lever arm and/or dial out the little peg that touches the idle microswitch itself so it pushes it in slightly earlier (and then when the engine is at full temp, and full vacuum, it's still pressing in enough to tell the idle speed motor to go.

[dmcnc]

I wouldn't mess with the adjustment (just yet) if it has never been touched. Being in Florida, you're pretty close to sea level and shouldn't need to adjust under normal circumstances. The fact that your car runs well when cold (richer thanks to the CPR) and runs jerky when warm tells me you might be running lean, vacuum leak being the most likely culprit. Could you get a dwell reading once at operating temperature and confirm? You should get a high reading if this is the case (above 50 - means its adjusting for lean)

[Parzival]

I would bet it's your idle microswitch not staying fully engaged once the engine is warm. Likely from a slightly weak or sticky return spring that's not quite strong enough to pull it back against the vacuum produced by a hot engine. You can try one of two things (or both): spray some lube in on the spring that sits at the pivot point of the idle microswitch lever arm and/or dial out the little peg that touches the idle microswitch itself so it pushes it in slightly earlier (and then when the engine is at full temp, and full vacuum, it's still pressing in enough to tell the idle speed motor to go.

I think that could be if it were not for the fact that I get a jerky acceleration especially if its under load, but its intermittent not always. While driving the microswitch is not supposed to be pressed anyway.


I wouldn't mess with the adjustment (just yet) if it has never been touched. Being in Florida, you're pretty close to sea level and shouldn't need to adjust under normal circumstances. The fact that your car runs well when cold (richer thanks to the CPR) and runs jerky when warm tells me you might be running lean, vacuum leak being the most likely culprit. Could you get a dwell reading once at operating temperature and confirm? You should get a high reading if this is the case (above 50 - means its adjusting for lean)

I don't have a dwell meter but I could get one if I had to. I had some vacuum leaks that were coming from the hose between the cold start valve and the idle sped motor back when I did the valley job, I got those tightened up, or at least enough so that I cant notice any hissing there. I put clamps at all connections.
I replaced all the vacuum routing when I did the valley job with Dana A.K.A DMC-81. All I hear people say about finding leaks is to spray carb cleaner around the connections and listen for a change. Is this reliable? I'd really like something more quantitative than that. Does anyone have a good recommendation a dwell meter? I've tried to explain this problem to DMC FL but unfortunately the car is always behaving perfectly whenever I'm there, go figure. They always tell me that my car is one of the best running cars they see, but then a few days later i'm driving and the jerky acceleration comes back. Through out the day, I'll make stops that let the car cool down, and I come back and she's perfect on startup and for the first few red lights, then she's warmed up and starts hunting a bit, and the jerky acceleration is back! If only I could get her to do it when the experts are looking. On a side not I think the problem presents it self a bit more noticeably now that the AC system is functional, because of the added load on the engine... just like to get this last thing figured out and she'll be pretty much all worked out mechanically... I hope

[dn010]

I bought a dwell meter off amazon. If you don't want to spend the money on something you'll hardly use, feel free to borrow mine if you want - although I can't recall if you're in or near Tampa or further away where it wouldn't make sense to get it.

[Parzival]

I bought a dwell meter off amazon. If you don't want to spend the money on something you'll hardly use, feel free to borrow mine if you want - although I can't recall if you're in or near Tampa or further away where it wouldn't make sense to get it.

thats awesome! I'm on the east cost so its a bit of a trek. Someone PMed with this recommendation a dwell meter, seems pretty inexpensive.
https://www.harborfreight.com/lcd-automotive-multimeter-with-tachometer-kit-95670.html

[FABombjoy]

I wouldn't buy a $40 dwell meter for this. Really you just need a duty cycle meter which can be had for less. Something like the UT136A should work.

The dwell meter is "utilized" because 1981 auto shops had them. Unless you really need to adjust ignition points I can't see the investment in a dwell meter being worth it.

D:04:09 even depicts and describes the system using duty cycle (0-100)

A dwell meter reads 0-90 and a DC reads 0-100, so you just have to change the manual's reference numbers accordingly:


35 38.9
45 50

40 44.4
50 55.6

87 96.7

20 22.2

50 55.6
60 66.7

[DMC1890]

If you've seen a video of someone measuring dwell on a Delorean, it always shows an Actron CP7605. I got mine from Amazon for $23, but they're no longer available there. You really want an analog meter for measuring things that are fluctuating. Unfortunately, after a quick search, I can't find anyone that still sells these.

[dn010]

+1, same meter I have. You can get them on eBay now for triple that price. Maybe I should sell mine. [emoji23]

[Parzival]

https://www.youtube.com/watch?v=ejUbEwtVw8E&feature=youtu.be

ok so, I needed a new multimeter anyway, so I got this one.
These are the readings cold and hot.
I sprayed carb cleaner around the vacuum connections and I never saw any effect. I didnt get any idle hunting today, that usually ony happens after driving a fair bit, but I did take it around the block and got some jerky acceleration. Can anyone make anything of these readings?

[DMC-81]

Hi Austin,

I have a Dwell Meter as well. If you're not in a hurry, we can check your dwell and other things at the next event etc.

http://dmctalk.org/attachment.php?attachmentid=59846&d=1556150271

[Parzival]

Hi Austin,

I have a Dwell Meter as well. If you're not in a hurry, we can check your dwell and other things at the next event etc.

http://dmctalk.org/attachment.php?attachmentid=59846&d=1556150271

yeah, that would be great! if I haven't tweaked this out yet by then. Or just let me know when you're free and I can always come out.
P.S. check my last post, I just posted a video of some reading I took.

[dmcnc]

Make sure you pull your readings on 4 cyl scale.





https://www.youtube.com/watch?v=ejUbEwtVw8E&feature=youtu.be

ok so, I needed a new multimeter anyway, so I got this one.
These are the readings cold and hot.
I sprayed carb cleaner around the vacuum connections and I never saw any effect. I didnt get any idle hunting today, that usually ony happens after driving a fair bit, but I did take it around the block and got some jerky acceleration. Can anyone make anything of these readings?

[Parzival]

Make sure you pull your readings on 4 cyl scale.

really? crap!

[dn010]

Keep in mind that vacuum leaks are not limited to the engine. You have vacuum lines running up to the front of the car, lines going to the vapor canister, etc.

[Jonathan]

Have you been inside your fuel tank before? What condition are things like in there? Perhaps that jerky acceleration is something blocking off or inhibiting the fuel pump suction.

[Parzival]

Have you been inside your fuel tank before? What condition are things like in there? Perhaps that jerky acceleration is something blocking off or inhibiting the fuel pump suction.

Yeah, It's possible, I forgot to mention that I had the problem before, and I replaced the spark-plugs and it went away, that was only a few months ago and now its back.
The fact that the problem is only present when the cars is hot would lead me to believe its not a fuel tank issue, but I suppose it could be. Perhaps I need to do the roter and wires too.

[Parzival]

Ok so here are the new readings,
Cold, the car starts right up runs smooth and drives fine. Then it warms up and clearly goes into a second mode, The dwell readings drop down to 10 or so, car still runs great, and drives fine. However after driving for a while it goes into a third mode, the dwell readings in this mode show it swinging from 10-25 or so, in the mode the car hunts and does not accelerate smoothly under load. In this final mode the only way to get a smooth ride is to keep the RPMs high by shifting late.

https://www.youtube.com/watch?v=s057tpzea-g&feature=youtu.be

[Bitsyncmaster]

Your mixture needs adjustment. Your running to rich. You get hunting because a warm engine runs with the idle motor almost closed and it has very little power to move the idle motor at closed locations. Try closing your curb idle screw a little more (turn CCW a little) after your adjust your mixture.

[dmcnc]

Like Dave said, your low numbers indicate rich setting (lean correction). I would adjust the curb idle by turning the curb idle screw up until the RPMs increase then back it off an 1/8 to 1/4 turn. You can use your RPM tachometer on your multimeter (this function is 6 cyl) hooked up to the coil wire to identify the spot where your RPMs increase.

If your dwell numbers stay the same afterwards, move on to CO adjustment, which will require you to VERY carefully drill out the CO adjustment plug. You will also need to make sure you have something to plug that hole after each adjustment and once the procedure is complete.

[Parzival]

Your mixture needs adjustment. Your running to rich. You get hunting because a warm engine runs with the idle motor almost closed and it has very little power to move the idle motor at closed locations. Try closing your curb idle screw a little more (turn CCW a little) after your adjust your mixture.


Like Dave said, your low numbers indicate rich setting (lean correction). I would adjust the curb idle by turning the curb idle screw up until the RPMs increase then back it off an 1/8 to 1/4 turn. You can use your RPM tachometer on your multimeter (this function is 6 cyl) hooked up to the coil wire to identify the spot where your RPMs increase.

If your dwell numbers stay the same afterwards, move on to CO adjustment, which will require you to VERY carefully drill out the CO adjustment plug. You will also need to make sure you have something to plug that hole after each adjustment and once the procedure is complete.

Thank you! I was worried that the numbers would be perfect and I'd still be on the hunt. This is promising, I'll carefully remove the plug and get to adjusting. Hopefully this solves the problem. I imagine that since car runs so well while the enrichment cycle is still going that there probably isn't something else going on... I hope

[Parzival]

Thank you! I was worried that the numbers would be perfect and I'd still be on the hunt. This is promising, I'll carefully remove the plug and get to adjusting. Hopefully this solves the problem. I imagine that since car runs so well while the enrichment cycle is still going that there probably isn't something else going on... I hope

Ok so I corrected the fuel mixture, it took only about a quarter turn.
But I'm still getting some jerky acceleration usually right around 20000 RPMs. I remember that I had this issue before, and I replaced the spark plugs and it seemed to fix the issue, but now its back. Cold it be that the rich condition messed up the spark plugs? Could my coil be going bad, rotor cap, or wires? Looks like I'm still going to be tinkering about with this.

[Ron]

A 1/4 turn on one that hasn't been tampered with is a lot!
Does it do OK above 20,000?

[Parzival]

A 1/4 turn on one that hasn't been tampered with is a lot!
Does it do OK above 20,000?
It might not have been that much to be honest, I just mean that it didn't have to be turned much, may have been a 1/16 of a turn.
but yes, its way better at higher RPMs. The dwell reading now swings right around 40-50. I guess the next step is to check fuel pressure?

[Ron]

It might not have been that much to be honest, I just mean that it didn't have to be turned much, may have been a 1/16 of a turn.
but yes, its way better at higher RPMs. The dwell reading now swings right around 40-50. I guess the next step is to check fuel pressure?

If you didn't answer that it was OK above 20K, I would have suspected that adjusting the CO compensated for a problem in the fuel system and went from there...

I would expect new plugs to clean up after driving around a bit. But at this point, I would double check the plugs (or install a set of AC Delco, if different than those installed when it ran OK before), vacuum leaks (use smoke), and all base settings (timing, at idle and at 20K; primary AND control pressures; etc). Then set the dwell where it swings 35-45, checking it with everything in place (including the breather and factory plug) and given a few seconds for things to settle after changing it.

A 1/16 turn is still a lot... To get an idea of how touchy it is- to change the dwell from the 40-50 you have to the 35-45 spec, expect to turn it as little as you can several times before you get it right.

If you get down to checking the coil, make sure you include shaking it. If you hear or feel the oil in it, toss it.

[Parzival]

If you didn't answer that it was OK above 20K, I would have suspected that adjusting the CO compensated for a problem in the fuel system and went from there...

I would expect new plugs to clean up after driving around a bit. But at this point, I would double check the plugs (or install a set of AC Delco, if different than those installed when it ran OK before), vacuum leaks (use smoke), and all base settings (timing, at idle and at 20K; primary AND control pressures; etc). Then set the dwell where it swings 35-45, checking it with everything in place (including the breather and factory plug) and given a few seconds for things to settle after changing it.

A 1/16 turn is still a lot... To get an idea of how touchy it is- to change the dwell from the 40-50 you have to the 35-45 spec, expect to turn it as little as you can several times before you get it right.

If you get down to checking the coil, make sure you include shaking it. If you hear or feel the oil in it, toss it.

So I was planning to install my new DMC fuel pump sender combo today but I had over half a tank. So I decided to just drive it all out. I took along my meter and an the 3mm allen wrench. After I drove for a while I hooked up the dwell and it was back to being rich, like I had never adjusted it. "what the heck! what is going on" so I adjusted it back to fluctuating around 45, and the jerky acceleration seemed to go away. "is it fixed? why did it revert back to being rich?"

Anyway, after that I drove around even more until the gas was low, and my old fuel pump started to get loud like it does when it gets hot.
Went back and started the process of installing the new pump. I uninstalled the old pump and the baffle. The boot had a nasty molasses like substance under it around the connections, and the pick up hose was all worm, soft and sticky. So I syphoned out the remaining gas, and dried the tank, and shop vaced it out. I made it like brand new in there, you could eat off of the inside of that tank now. I finished the installation, filled the tank, and took to the streets. Seems to be running good now. Dwell reading are correct, and wasn't getting any jerky acceleration. Idle is steady right form start up. the only thing I can say now is that there my be a bit of vibration at idle. This may be normal? I Only notice it when the AC is on. maybe the extra load I guess. Anyway I will continue to test and all that.
Next week I'm going to be replacing the lines to my FV with SSlines, and the send and return lines, which will complete the conversion to all SSlines in my engine compartment, no more plastic lines.
If anyone has any ideas about why the mixture adjustment seemed to have reset it self, let me know.

[dn010]

Dumb question, but are you plugging the CO adjustment screw hole after you make the adjustments and go for a drive?

[Parzival]

Dumb question, but are you plugging the CO adjustment screw hole after you make the adjustments and go for a drive?

I am,
I only remove the plug long enough to make the adjustment then replace it to check the result.
It's not a dumb question, if someone where doing that it would be important to know in order to help them :) Assuming they already know could cause something like that to be overlooked. So from here on out there are no dumb questions :) Assume I know nothing, and I promise not to be insulated. lol

[Ron]

After I drove for a while I hooked up the dwell and it was back to being rich, like I had never adjusted it. "what the heck! what is going on" so I adjusted it back to fluctuating around 45, and the jerky acceleration seemed to go away. "is it fixed? why did it revert back to being rich?"

Intermittent vacuum leak?

We pulled hair on one where the dwell would randomly change after a day, weeks, no telling...
Long story short- The roller that the FD's plunger rides on had seized up from sitting for years. Later, a flat spot wore on the roller. Then it freed up (some)...

Curious as to why you keep setting the dwell to 45° instead of 40°?

[Parzival]

Intermittent vacuum leak?

We pulled hair on one where the dwell would randomly change after a day, weeks, no telling...
Long story short- The roller that the FD's plunger rides on had seized up from sitting for years. Later, a flat spot wore on the roller. Then it freed up (some)...

Curious as to why you keep setting the dwell to 45° instead of 40°?

because I'm ad idiot and thought thats what it was supposed to be set at. LOL
I'm sure I'm no done adjusting it. I'm going to change those remaining lines in the engine compartment this week, and then I'll make a new adjustment. I can't find a leak, at least not with carb cleaner.
When I change the lines to the FV is there a way to clean the FV while I have it out? Is this a good idea?
Thanks

[Ron]

because I'm ad idiot and thought thats what it was supposed to be set at. LOLLMAO ...but, but, I mentioned that before :deviltail:



When I change the lines to the FV is there a way to clean the FV while I have it out? Is this a good idea?

Unless your D has sat a long time with fuel in it recently, I'd say just make sure there is no foreign material in the FV's ports when you put it all back together.
Maybe do the whole system by dumping a good injector cleaner in the tank...and have fun running it out on the road.

[DMC-81]

When I change the lines to the FV is there a way to clean the FV while I have it out? Is this a good idea?
Thanks

Hi Austin. Yes, I cleaned out my Frequency Valve. You can find details in post #6 of this thread:

http://dmctalk.org/showthread.php?17149-Replacing-the-Frequency-Valve-and-Return-hoses

[Parzival]

LMAO ...but, but, I mentioned that before :deviltail:



Unless your D has sat a long time with fuel in it recently, I'd say just make sure there is no foreign material in the FV's ports when you put it all back together.
Maybe do the whole system by dumping a good injector cleaner in the tank...and have fun running it out on the road.

Well it sat for 9 years before I got it last year, but hasn't sat for more than a week since. I'll probably put a can of seafoam through it once all the lines are done. I don't want to break a deposit loose from the inside of an old line and have it head straight for the FV or and injector!
You said set the Dwell for 40? I need to read harder lol. So when I do these lines this week I will install the new fuel filter too. I'm sure all this fussing around it there might effect the mixture, and I'll reset it when all is done (this week) I'm also about to re do the fues block, got that kit from DMCFL when I bought the fuel pump. I'm still not convinced that this could all be electrical. I'll clean all the major grounds while I'm at it.

[Parzival]

Hi Austin. Yes, I cleaned out my Frequency Valve. You can find details in post #6 of this thread:

http://dmctalk.org/showthread.php?17149-Replacing-the-Frequency-Valve-and-Return-hoses

Awesome, and what about the wur?

[DMC-81]

Awesome, and what about the wur?

Yes, I cleaned that screen too, same procedure ( I used cotton swabs soaked in carb cleaner to clean the brass screen and the other fitting):

Before:
http://dmctalk.org/attachment.php?attachmentid=44938&d=1469836685

After:
http://dmctalk.org/attachment.php?attachmentid=44940&d=1469836882

It's also a great time to check/replace the vacuum lines ( although I think you possibly did that during the VOD job.. I can't remember).

[Parzival]

Yes, I cleaned that screen too, same procedure ( I used cotton swabs soaked in carb cleaner to clean the brass screen and the other fitting):

Before:
http://dmctalk.org/attachment.php?attachmentid=44938&d=1469836685

After:
http://dmctalk.org/attachment.php?attachmentid=44940&d=1469836882

It's also a great time to check/replace the vacuum lines ( although I think you possibly did that during the VOD job.. I can't remember).

alright! now we're talking! we did replace the vac lines. but I don't remember if we cleaned out the wur. I don't think we did.

[Parzival]

is this the correct fuel pressure test kit?
https://www.amazon.com/Tool-Aid-33865-K-Jetronic-Injection/dp/B0002SR5NU/ref=asc_df_B0002SR5NU/?tag=hyprod-20&linkCode=df0&hvadid=312174136943&hvpos=1o1&hvnetw=g&hvrand=8657985049139506279&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9011833&hvtargid=aud-643191255296:pla-568038596040&psc=1&tag=&ref=&adgrpid=63790029762&hvpone=&hvptwo=&hvadid=312174136943&hvpos=1o1&hvnetw=g&hvrand=8657985049139506279&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9011833&hvtargid=aud-643191255296:pla-568038596040

[Ron]

That looks like a good one.

Remember to get extra copper seals...

[Parzival]

That looks like a good one.

Remember to get extra copper seals...

Check, I got a big bag of em