Stumbling/Stalling during Idle

[Mattglas]

Up until last month my car ran perfectly, it idled at 750 and never stumbled. However, out of nowhere it started to stumble and then stall whenever it idles (hot or cold). I've thrown everything I can think of at it and nothing has worked. Does anyone have any sugestions?

Here's a list of the things I've done:

New gaskets/o-rings on top end of engine
Readjusted the valves
Adjusted the timing
Checked the spark plugs
Checked the dwell swing
Checked compression (115psi cold on everyone)
Checked voltage to idle motor (11v)
Checked idle ecu and motor by removing the plug closest to the center of the car and having the idle spike to 2200
Checked battery voltage at idle (13.5

to 14.5)

This is what happens when the car idles:

https://drive.google.com/file/d/0B2N21dp4QgiGNDFMbVV1aFBlZGs/view?usp=drivesdk

Don't know if its related but is this amount of smoke coming out of the oil filler normal?

https://drive.google.com/file/d/0B2N21dp4QgiGV0ZsWFNDYVVLS0U/view?usp=drivesdk

[Bitsyncmaster]

Does it just the idle problem? Does it run normal when driving?

I would do a fuel pressure check.

Sudden problems could be the fuel pump but that would also show a problem when driving.

[Mattglas]

Does it just the idle problem? Does it run normal when driving?

I would do a fuel pressure check.

Sudden problems could be the fuel pump but that would also show a problem when driving.It runs fine while driving, doesn't misfire or hesitate at all. I replaced the fuel pump a few months ago with the updated combo one. Relating to fuel, I have 93 octane in the tank. Not sure if that makes a difference. I just recently found out that it requires 87.

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[Bitsyncmaster]

It runs fine while driving, doesn't misfire or hesitate at all. I replaced the fuel pump a few months ago with the updated combo one. Relating to fuel, I have 93 octane in the tank. Not sure if that makes a difference. I just recently found out that it requires 87.

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Now I don't think the fuel is the problem. What voltage does your car hold at idle speed?

[Mattglas]

Now I don't think the fuel is the problem. What voltage does your car hold at idle speed?It starts at 14.5v and slowly decreases to 13.5v and then goes back up to 14.5v. I have specialtautos 120 alternator.

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[Bitsyncmaster]

Does the voltage drop to 13.5 because the RPM is dropping? Just looking for clues to help find your problem. Seems odd it starts out at 14.5 volts unless your engine RPM is higher during that time.

[Mattglas]

Does the voltage drop to 13.5 because the RPM is dropping? Just looking for clues to help find your problem. Seems odd it starts out at 14.5 volts unless your engine RPM is higher during that time.The rpm stayed between 600 and 725 the whole time I was testing. I don't really remember if it was related to the rpm droping. I think the voltage was just decreasing and increasing

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[Bitsyncmaster]

I looked back at your video and it looked like the oil pressure gauge was jumping without the RPM changing much. How old is your battery? I'm still just guessing at what may be the problem. An idle only problem like you have is strange since you have verified the mixture (dwell) is good.

One thing I just thought of is I have seen some RPM relays have marginal connections on the second output which drives the lambda system. But that problem is only with RPM relays that have the twin contacts on the relay. I would just jumper the RPM relay (three pin jumper) to test if the problem goes away. That problem may not show up at higher engine RPM.

[Mattglas]

I looked back at your video and it looked like the oil pressure gauge was jumping without the RPM changing much. How old is your battery? I'm still just guessing at what may be the problem. An idle only problem like you have is strange since you have verified the mixture (dwell) is good.

One thing I just thought of is I have seen some RPM relays have marginal connections on the second output which drives the lambda system. But that problem is only with RPM relays that have the twin contacts on the relay. I would just jumper the RPM relay (three pin jumper) to test if the problem goes away. That problem may not show up at higher engine RPM.The battery is around a year old. The jumping oil pressure is also a new occurrence, started around the same time. Though, I thought it was due to the original oil pressure sender that my car has. For jumping the rpm relay I would jump pins 30, 87, and 87b right?


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[Bitsyncmaster]

The battery is around a year old. The jumping oil pressure is also a new occurrence, started around the same time. Though, I thought it was due to the original oil pressure sender that my car has. For jumping the rpm relay I would jump pins 30, 87, and 87b right?


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You would jump the large brown wire (+12 volts) to the white/purple (pump) and the double yellow/red (lambda).

I don't look at pin numbers much anymore.

[Mattglas]

You would jump the large brown wire (+12 volts) to the white/purple (pump) and the double yellow/red (lambda).

I don't look at pin numbers much anymore.Ya, those are the ones. I'll have to check it out once I get back home

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[Jonathan]

Any reason to think your inertia switch has gone bad? There was an old recall on those that replaced the switch and/or moved it to a slightly different location. If you have the replacement inertia switch, it'll have a white mark on it and it'll be mounted over on the sidewall and not together with the lambda counter. Maybe it failed inside or it might just be a poor connection. That'll make the fuel pump cut out if so. Although that video showing your oil pressure gauge makes me think it's something electrical back at the engine and not up at the fuel pump. Perhaps double check all your electrical connections are good and clean and tight on the ignition coil as well as the ballast resistor.

[Mattglas]

Any reason to think your inertia switch has gone bad? There was an old recall on those that replaced the switch and/or moved it to a slightly different location. If you have the replacement inertia switch, it'll have a white mark on it and it'll be mounted over on the sidewall and not together with the lambda counter. Maybe it failed inside or it might just be a poor connection. That'll make the fuel pump cut out if so. Although that video showing your oil pressure gauge makes me think it's something electrical back at the engine and not up at the fuel pump. Perhaps double check all your electrical connections are good and clean and tight on the ignition coil as well as the ballast resistor.My inertia switch was bypassed by the PO. So I'm not sure if that would effect it. I will double check the electrical connectors though, maybe hit them with some sand paper.

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[DMC5180]

The engine was certified to run on Standard 87 octane. Running a higher grade only hurts your wallet, not the engine. If you had a Stage II upgrade then it would be necessary to run 91 or better due to slightly higher compression ratio.

I had a randomly twitchy oil pressure gauge for quite a long time. Replacing the sender did not fix the issue. Cleaning The PCB contacts to the gauge did fix it.

for some reason I was not able to see you first video. Just going by what Dave said.

[Elvis]

are you sure your idle system is working at all ?

looks like the ISM motor is freezed an can not react on load changes

[DaraSue]

How old is your idle speed motor? I had a newer one go bad due to flaky wiring on the inside not making a consistent connection.

[Mattglas]

How old is your idle speed motor? I had a newer one go bad due to flaky wiring on the inside not making a consistent connection.It's the original motor that came with the car. Is there any tests I could try to see if it's the problem?

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[DaraSue]

It's the original motor that came with the car. Is there any tests I could try to see if it's the problem?


Mine was in the shop when they found it, but IIRC we could actually feel it running jumpily when we touched it.

[DMC5180]

In order to test the ISM too see if it is not stuck. Pull the Little connector hose off the ISM side. The Brass pipe with the Cold start valve will move, swing toward you about a half inch.
It is just enough to pull the hose off the ISM port. let the hose sit to the side of the ISM port. Use a flashlight or be in a well lit area that allows you to see in the port. Turn the Key to the Run position and observe what the valve does. You are looking for smooth movement of the valve. If it is Stuck, then it won't move at all of course. If it moves in a shuddery motion, it is sticking. you may be able to free it up by spraying a solvent cleaner through it. Then lube the pivot bearing withe light machine oil. 3 in 1 oil is good all purpose household oil to use. it won't evaporate like penetrating oils does.

Here is a video I took of mine several years ago. Direction the valve moves to open an close just depends on how it is mounted. It can be either direction.

https://youtu.be/fUOK0ksB0Gs

[Mattglas]

In order to test the ISM too see if it is not stuck. Pull the Little connector hose off the ISM side. The Brass pipe with the Cold start valve will move, swing toward you about a half inch.
It is just enough to pull the hose off the ISM port. let the hose sit to the side of the ISM port. Use a flashlight or be in a well lit area that allows you to see in the port. Turn the Key to the Run position and observe what the valve does. You are looking for smooth movement of the valve. If it is Stuck, then it won't move at all of course. If it moves in a shuddery motion, it is sticking. you may be able to free it up by spraying a solvent cleaner through it. Then lube the pivot bearing withe light machine oil. 3 in 1 oil is good all purpose household oil to use. it won't evaporate like penetrating oils does.I did the test and this is what I found. When the key was turned the valve instantly turned all the way to the right (right being towards the center of the engine). Then, it held that position for about 10 seconds and slowly/smoothly went back to the original position.

I also noticed that the inside of the valve was coated with black soot.

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[DMC5180]

I did the test and this is what I found. When the key was turned the valve instantly turned all the way to the right (right being towards the center of the engine). Then, it held that position for about 10 seconds and slowly/smoothly went back to the original position.

I also noticed that the inside of the valve was coated with black soot.

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the black soot it normal but you can clean it. Was movement fairly smooth. Movement you observed would be Normal, so long as it didn't stutter during the sweep.

[Mattglas]

the black soot it normal but you can clean it. Was movement fairly smooth. Movement you observed would be Normal, so long as it didn't stutter during the sweep.It didnt really stutter, though the movement did get faster towards the end of it's travel.

I also noticed the mine seemingly has a bigger gap than yours. I included a picture just for comparisonhttps://uploads.tapatalk-cdn.com/20170730/c058b03ee7423f4241a8d91bc6ca3a12.jpg

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[Bitsyncmaster]

The stock idle ECU does not ever close the valve (idle motor) all the way. When I had the stock ECU it closed a little more than in your photo. But all that means is you have a little less control for holding the 775 RPM on a hot engine.

[Mattglas]

A video is probably better:

https://drive.google.com/file/d/0B2N21dp4QgiGdktvanNsdGJiNFk/view?usp=sharing

[Mattglas]

The stock idle ECU does not ever close the valve (idle motor) all the way. When I had the stock ECU it closed a little more than in your photo. But all that means is you have a little less control for holding the 775 RPM on a hot engine.

Oh, interesting. This bit off topic, but do you still sell your microprocessor controlled idle ECU? I remember seeing it awhile ago and wanting to upgrade.

[Bitsyncmaster]

Oh, interesting. This bit off topic, but do you still sell your microprocessor controlled idle ECU? I remember seeing it awhile ago and wanting to upgrade.

Yes, I still sell them. My ECU will close the valve completely if needed. That was one of the things I did not like about the stock unit and my car would idle at 1000 RPM when hot. But that turned out to be bad deceleration springs on the butter fly valves.

Here is a video I did when I designed my ECU.

https://www.youtube.com/watch?v=8YE_HG4ji8E

[Mattglas]

Yes, I still sell them. My ECU will close the valve completely if needed. That was one of the things I did not like about the stock unit and my car would idle at 1000 RPM when hot. But that turned out to be bad deceleration springs on the butter fly valves.

Here is a video I did when I designed my ECU.

https://www.youtube.com/watch?v=8YE_HG4ji8E

Sweet, once I get this issue fixed I'll pm you about buying one.


In other news, while testing I noticed that when the cooling fans came on the car would suddenly start to idle hunt. Once the fans stopped the idle hunting stopped. Possible ground issue?

[Mattglas]

I took the car for a 10 minute drive and when I got back I let it idle to see what wolud happen. After a few minutes it stumbled itself to death and I was greeted with this:

https://drive.google.com/file/d/0B2N21dp4QgiGbVAtbHZhVl84Wlk/view?usp=sharing

I'm not sure what to make of it.

[DMC5180]

what did the smoke smell like? How much resistance was their when you first pushed down on the air plate? Pushing down that far would dumped fuel into the hot heads and any valve that was open. It could have just been fuel boiling off. or oil residue in the intake from crankcase venting. worst case would be coolant vapor steaming off. It just depends on what smell like as to what it might be.

[Bitsyncmaster]

With it stumbling to a stop, you probably have miss fires and some of the intake valves are open. So I would think that "smoke" is unburned fuel.

[Mattglas]

what did the smoke smell like? How much resistance was their when you first pushed down on the air plate? Pushing down that far would dumped fuel into the hot heads and any valve that was open. It could have just been fuel boiling off. or oil residue in the intake from crankcase venting. worst case would be coolant vapor steaming off. It just depends on what smell like as to what it might be.It didn't really smell like anything and the plate had pressure everytime I pushed on it. It probably was fuel boiling off.

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[DMC5180]

It didnt really stutter, though the movement did get faster towards the end of it's travel.

I also noticed the mine seemingly has a bigger gap than yours. I included a picture just for comparisonhttps://uploads.tapatalk-cdn.com/20170730/c058b03ee7423f4241a8d91bc6ca3a12.jpg

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I should have mentioned that I have Dave's Idle ECU. that's why mine Closed all the way before popping open.

[lazabby]

Sweet, once I get this issue fixed I'll pm you about buying one.


In other news, while testing I noticed that when the cooling fans came on the car would suddenly start to idle hunt. Once the fans stopped the idle hunting stopped. Possible ground issue?

My car is hunting with the AC on. Might be a similar issue as yours. I have new plugs, new fuel injectors, new CO2 sensor. I may need to tweak the idle with the dwell meter.

[David T]

My car is hunting with the AC on. Might be a similar issue as yours. I have new plugs, new fuel injectors, new CO2 sensor. I may need to tweak the idle with the dwell meter.

You cannot "fix" the idle by adjusting things. If the idle is hunting a lot (some is normal) it is because of some imbalance among the 6 cylinders. As it comes around to the weaker one the motor slows down and then speeds up as it fires on the next, more powerful one. Something is different among the cylinders, a spark plug gap, a valve adjustment, a bad ignition wire, something that makes one or more cylinders less efficient. Just because you have new parts does not mean they are all the same. Especially the fuel injectors.

[Mattglas]

Today I was thinking about Bitsyncmaster's post on how sudden problems could be the result of the fuel pump. So, I decided to check it out. Which was a good idea, judging by all the rotten plastic clogging it.

52646526475264852649

I'm not really sure how any of it got there. The first thing I did when I purchased my car was clean the fuel tank.

[Jonathan]

Today I was thinking about Bitsyncmaster's post on how sudden problems could be the result of the fuel pump. So, I decided to check it out. Which was a good idea, judging by all the rotten plastic clogging it.

52646526475264852649

I'm not really sure how any of it got there. The first thing I did when I purchased my car was clean the fuel tank.

And did you get your car fairly recently?

If you put that new fuel pump/sender combo into a clean tank, that debris would need to have either been part of something else already in the system or introduced through one of the openings.

New material can obviously come into the fuel system by way of filling up at the gas station. Not likely that it's in the gas you're buying, but maybe down through the fuel filler cap. Some piece of plastic that was being used to cover things being painted perhaps?

Existing material might be part of the inside of some hose that's deteriorating. Or plastic wrap not realized was still on a new part like the fuel pump/sender combo unit or even the fuel sender hole filler cap (the one not used anymore with the combo set-up). I've seen packaging mistakenly left in systems in industrial environments so it could happen with our cars too.

Another possibility might be the fuel filler neck when you did your cleaning was hiding a mess of spider webs or other bug or critter debris. If that wasn't noticed and then everything got buttoned back up and the tank filled with fresh gas, it could have flushed it all in there. Same too with the smaller lines for the roll over valve (although less likely as they're pretty small and don't have any "flow" through them).

Based on the volume of comments I see or hear from people with fuel tank contamination, I'd guess it was an old hose disintegrating that left you with this mess. I've not seen my own evidence of that first hand, so take it with a grain of salt, but it does get mentioned frequently.

[Mattglas]

And did you get your car fairly recently?

If you put that new fuel pump/sender combo into a clean tank, that debris would need to have either been part of something else already in the system or introduced through one of the openings.

New material can obviously come into the fuel system by way of filling up at the gas station. Not likely that it's in the gas you're buying, but maybe down through the fuel filler cap. Some piece of plastic that was being used to cover things being painted perhaps?

Existing material might be part of the inside of some hose that's deteriorating. Or plastic wrap not realized was still on a new part like the fuel pump/sender combo unit or even the fuel sender hole filler cap (the one not used anymore with the combo set-up). I've seen packaging mistakenly left in systems in industrial environments so it could happen with our cars too.

Another possibility might be the fuel filler neck when you did your cleaning was hiding a mess of spider webs or other bug or critter debris. If that wasn't noticed and then everything got buttoned back up and the tank filled with fresh gas, it could have flushed it all in there. Same too with the smaller lines for the roll over valve (although less likely as they're pretty small and don't have any "flow" through them).

Based on the volume of comments I see or hear from people with fuel tank contamination, I'd guess it was an old hose disintegrating that left you with this mess. I've not seen my own evidence of that first hand, so take it with a grain of salt, but it does get mentioned frequently.

I think the debris must have come from the fuel filler tube. I couldn't find anything else that could have caused it.

[Mattglas]

I did some fuel injector testing in order to rule them out as a problem. I'm not really sure what to make of my findings, the amount of fuel in each container varied on every test I did.
I pushed the plunger down fully for 1 min and checked if each container reached the 6oz mark. Some times they did and sometimes they didn't. Could this be a problem with the fuel distributor? I changed the injectors around and still got the same results.

First test:
52751

Third Test:
52752

[Bitsyncmaster]

I did some fuel injector testing in order to rule them out as a problem. I'm not really sure what to make of my findings, the amount of fuel in each container varied on every test I did.
I pushed the plunger down fully for 1 min and checked if each container reached the 6oz mark. Some times they did and sometimes they didn't. Could this be a problem with the fuel distributor? I changed the injectors around and still got the same results.

First test:
52751

Third Test:
52752

Try running the test pushing the air plate about half way down. I had one cars test really have a problem pressed fully.

[Mattglas]

Try running the test pushing the air plate about half way down. I had one cars test really have a problem pressed fully.I redid the test pushing halfway down and found that the inconsistency goes away. However, they are not exactly even. Some have a just a bit more gas in them.https://uploads.tapatalk-cdn.com/20170810/24bef05a21870dd717c1fc1351185c89.jpg

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[David T]

Run a full tank of fuel and a can of Techron and then redo the test. That should clean things up and make it more even. Wil also help with the fuel injectors.

[Bitsyncmaster]

I redid the test pushing halfway down and found that the inconsistency goes away. However, they are not exactly even. Some have a just a bit more gas in them.https://uploads.tapatalk-cdn.com/20170810/24bef05a21870dd717c1fc1351185c89.jpg

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Those look pretty good. Unless you have the adjustable FD type, I would not worry about adjusting the FD with shims.

[NckT]

Just double check that the small filters in the firm distributor are clear. Remove and back flush them if necessary. These can cause a flow restriction. There is one per injector fuel line under the hollow bolt.

A variance of 5% is allowable for full flow (venturi flap pushed fully down) for the volumetric test.

[NckT]

"Fuel Distributor", not "firm distributor"