M20 Stalling When Warm/ Operating Temperature

[Jdbush2010]

I found this kinda interesting (the first line) when I was going threw the records. I guess the car was brought into the dealership and they replaced the fuel pump AND its connector. I'll take a look at it but like I've said many time's, the car has a really smooth idle when you first start it, then a couple minutes later it'll become rougher until it finally start's stalling on you when you tap the throttle pedal, or come to a complete stop at a light (basically whenever you bring the car back to idle from when then engine was just being rev'd). The car still has a hesitant idle that you can hear when warm, but usually won't stall until you tap the throttle pedal... Occasionally will stall on its own at idle.




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These were my exact symptoms, not dying but idling right around 450-500. Except I've gotten it kinda controlled now with the crankshaft sensor. It still wants to idle rough but I'm getting on the upper side of the fight. I don't know if you checked that or not

[Bullet Ride]

That's a good catch, there could be a botched solder that worked ok for a while but is now cracked or separating.

[KIRIEIW]

I found this kinda interesting (the first line) when I was going threw the records. I guess the car was brought into the dealership and they replaced the fuel pump AND its connector. I'll take a look at it but like I've said many time's, the car has a really smooth idle when you first start it, then a couple minutes later it'll become rougher until it finally start's stalling on you when you tap the throttle pedal, or come to a complete stop at a light (basically whenever you bring the car back to idle from when then engine was just being rev'd). The car still has a hesitant idle that you can hear when warm, but usually won't stall until you tap the throttle pedal... Occasionally will stall on its own at idle.




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[KIRIEIW]

M20 Stalling When Warm/ Operating Temperature

TPS is working and in spec


Edit: decided to just take the throttle body off and clean it. Was pretty clean, light amount of oil but I've seen much worse on m20's. I was able to instal my new throttle body gasket though so that was nice. Crappy pic of before I cleaned it.



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[KIRIEIW]

I actually did a timing belt job for a buddy just last week, along with a few other things and the breather hose was one of them. He didn't have a new breather hose to put back on the car and he chanced it and drove it home with NO hose attached. Ran great for him, in fact a lot of 2002 guys just put a little air filter deal on the valve cover where the breather hose nipple is with no issues. With that being said, I got a new breather hose from work for him the next day and installed it for him. I don't think vacuum leaks from the Valvetrain area effect the car much, if at all that breather hose is there just to help with emissions (I hope so anyways otherwise I'm looking like a dummy here).

I just installed the new coolant temp sensor with no change, looks like it's time to test the TPS. It does click, so I need to test its resistance with the specs the Bentley calls for.


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[Som]

I've forgotten to put my oil cap back on before after adding oil, the car was only idling slightly rough. It definitely wasn't anywhere near stalling out.

That's my recollection from how my E36 behaved, but I don't know if I ever really waited for it to warm up or anything.

I think this might only true if your TPS is functioning because if the idle switch isn't made then the DME won't trigger the idle table (which the car can run on with the AFM unplugged)

Makes sense. That made me realize -- I guess yet another way to test is to unplug the TPS completely and just short the middle+idle pin in the plug with a paperclip or something. If that fixes the idle, then the TPS is busted.

Som

[Bullet Ride]

have someone with a working E30 loosen their oil cap and see if it exhibits the same symptoms.

I've forgotten to put my oil cap back on before after adding oil, the car was only idling slightly rough. It definitely wasn't anywhere near stalling out.

I was under the impression you could even just disconnect the AFM/O2/Coolant Temp sensors and still expect to have the engine idle since the ECU would be able to substitute default values.

I think this might only true if your TPS is functioning because if the idle switch isn't made then the DME won't trigger the idle table (which the car can run on with the AFM unplugged)

[Som]

Few things from my perspective. Not sure how helpful, but who knows...

The TPS test is pretty easy if you have a continuity tester or ohmmeter. There's 3 pins. The middle one is a common pin. When the throttle is closed, you should see continuity with one of the pins, and when the throttle is about 2/3rds to WOT, you should see continuity between the middle and the other pin.

Before doing that, though, I'd first check to see if you can feel a noticeable click when you close the throttle by hand. Open the throttle by hand and slowly release it. Just before it hits its resting point you should feel a click. If it's not there, that's a problem. Remove your throttle cable and try again -- if you feel the click now, then your throttle cable might be too tight. That said, just having a click doesn't mean you're problem free -- you'd still need to do the above continuity test because the idle switch inside the TPS could be bad.

Regarding the camshaft plug leak. I'm not really that experienced with the specific symptoms of vacuum leaks and all that. I will say, though, to keep in mind that the valve cover has a breather hose that connects to the throttle body. So, conceivably, a camshaft plug leak is still a leak that affects your intake pressure. One way to test the significance would be to have someone with a working E30 loosen their oil cap and see if it exhibits the same symptoms.

It seems like there'd only be a handful of likely sources to the problem you're describing, and I'd think the ICV would be one of them. TPS and intake leaks would be the other two. Not saying there can't be a million reasons (right down to the dreaded wiring harness possibility), but I think there's definitely more testing to do with the most likely suspects first. I believe all the other failure items are things the ECU is supposed to be able to deal with. I was under the impression you could even just disconnect the AFM/O2/Coolant Temp sensors and still expect to have the engine idle since the ECU would be able to substitute default values.

Given that, despite the ICV being cleaned and buzzing, I'd see if I can borrow someone's known good one to test with.

Good luck. Curious to hear what it turns out to be. Fortunately I haven't had to deal with any idle gremlins yet, but it's good to have data points so I know where to go when I do. :)

Som

[KIRIEIW]

Ok, I watched the video and it looks like as soon as you released the throttle, the air is cut off from the engine. Have you cleaned the throttle body and plate?

I have not! I planed on cleaning it this weekend (my work keeps me from morning to night so there's sadly no time to do work on the week days.) I have an extra throttle body gasket already so I'll swap that in at the same time. I had the boot off and was able to see inside the throttle body a few weeks ago, little oily inside and I gave it a quick whip but didn't bother cleaning the pivoting points for the butterfly flap. I know the Bentley calls for lubricating the throttle body every so and so miles. Also, your right the car does only stall whenever the throttle is released completely, when operating temperature.

I picked up a used TPS at the junkyard after Bullet Ride's suggestion. Oily as hell but I sprayed a ton of contact cleaner inside hoping to clean most of the oil up that got inside. In case mine is out of spec, I'll now have an extra to swap in and test.

[KIRIEIW]

Check DME main relay (I once had one work great at higher RPM's but not at lower).
Check the pulse generator wire off of the spark plug wires
Load test the battery to confirm if you have a dead cell (also monitor voltage when driving).

How did you check the CPS?

I have an extra DME relay so I'll swap my extra in and report back

Is there a spec to check the pulse wire resistance in the Bentley? I'll look at my book later today. I always thought your car would still run with that wire disconnected, I know the 325e's don't have one.

I'm assuming the battery's good because it was replaced about 6 months ago, and I also have a receipt for a new alternator a few years back. I suppose it's still possible but I highly doubt it.

[dnguyen1963]

Ok, I watched the video and it looks like as soon as you released the throttle, the air is cut off from the engine. Have you cleaned the throttle body and plate?

[noid]

Check DME main relay (I once had one work great at higher RPM's but not at lower).
Check the pulse generator wire off of the spark plug wires
Load test the battery to confirm if you have a dead cell (also monitor voltage when driving).

How did you check the CPS?

[KIRIEIW]

Took a quick video, this is the second time I decided to take the car for a spin because it stated and idled great when cold. Huge mistake, once it gets warm it stalls out at every stop sign and I get strand for a few minutes at a time. Once the car is moving however, it runs pretty good (its starting to have a few stumbles when driving/moving but it doesn't flat out stall).

I have a new temp sensor coming in the mail, the specs for the Bentley show a resistance value when the cars fully warmed up, and I'm not 100% sure if it's even getting to full operating temp. so testing it wouldn't be completely accurate.

Today I swapped ECU's (Junkyard got a 1991 Automatic yesterday so I ran over there today before anyone could grab it), cleaned all the plugs/ sensors I could reach in the engine bay with contact cleaner, checked the C191 and C101, both where in perfect shape with no visible corrosion but cleaned anyways. Also unplugged the O2 sensor, the car ran with it disconnected but still had the same problem.. found it weird however the check engine light wasn't illuminated with it being disconnected.


Link to video:
https://www.youtube.com/watch?v=vZ9YKU7oiC4

[KIRIEIW]

Bought a used ECU today and swapped it out, same problem.


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[noid]

Check the main relay, CTS and DME. You are correct that disconnecting the O2 sensor will make the car run off a default map.