Stumbling/Stalling during Idle

[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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