Mechanics

STALLS WHEN TRYING TO START WARM ENGINE

1997 Buick Lesabre • 127,000 miles

I had diagnostic done, no problems with the sensors as far as readings etc.
no vacuum leaks, no bad connections, no codes pending or stored.
car starts right up when it is cold, once engine is warm it will immediately shut off when it is started a few times before it finally stays running, the tach will fluctuate between 1000 and 1500RPM a few times before it settles at around 700, after that it runs perfectly and drives great. If I let it sit until engine is cold it will again start and run great 1st try.
fuel pressure is right on the money. Everyone who has tried to figure it out is stumped, was also told that if it was the PCM the car would never run right.
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Pcdj64
May 16, 2012.




Try cleaning the throttle plate with choke cleaner on both sides and make sure no holes in air ducts.

Tiny
Hmac300
May 16, 2012.
Brand new upper intake was installed and throttle body is like new.
There are no leaks anywhere

Tiny
Pcdj64
May 16, 2012.
The only thing I can think of is to check cam and crank sensors for ohms. It may get hot and not want to run right or have to many ohms creating to much resistance. We dont' have info for them so check against new. Or if someone has a resistance chart for those.

Tiny
Hmac300
May 16, 2012.
I could check the sensors, it is worth a shot.
I can get the values to go by for the resistance.
If I hold the gas a tiny bit when I start it it will stay running.
I changed the IAC and TPS and they test good.
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Tiny
Pcdj64
May 16, 2012.
Well the cam and cranks sensors alot of times won't set a code bu still can be screwed up. Also with the fuel pressure did you check it after the engine was off and let it sit to see what happened?

Tiny
Hmac300
May 16, 2012.
It had a problem last month with fuel pressure, the pump was shot and I ended up getting a new tank, sending unit with the pump, filler neck, fuel filter and pressure regulator, I opened a can of worms with the rust that was on the old stuff.
The regulator was changed because the old one was malfunctioning.
I know the sensors can be bad even without a code, I ran into that with the MAF. The garage initially told me to change the TPS because with very little pressure on pedal it will stay running, you release and it goes to 700RPM. It is a very nice running engine, tons of pickup and smooth. Only issue is starting, I am not an expert by far but it almost seems like the PCM is not picking up the initial pulse from the crank sensor to start the firing order and holding the pedal a little gets the engine to stay on long enough for it to catch up. Probably way off but it is an educated guess anyway lol.

Tiny
Pcdj64
May 16, 2012.
To add to the already screwed up car, it has 3 new premium quality coils, new bosh premium wires and irridium spark plugs, the PCM is not reporting a misfire but there is one, engine is running a little bit rough and you can hear the miss when you are at the back of the car. It is running on all 6 and has power.

Tiny
Pcdj64
May 17, 2012.
I exchanged the plug wires for new ones under warranty, seems to have gotten rid of the misfire.
No one can tell me why the car will not stay running when I start it warm, with all of the work done it will no longer shoot up to high idle or fluctuate much on the tach but unless I put a little pressure on the gas it will not keep running when it is started warm. After about 10 seconds I can release gas and it runs fine until next time I have to start it again. Always starts fine cold.
No check engine light, no vacuum leaks, no bad connections, fuel pressure is where it should be, plenty of power. Everyone is stumped, the only thing that it could be is a bad PCM I am being told. I looked at the PCM there is a little panel with 2 hex screws, is that where the chip is to switch to a new PCM?

Tiny
Pcdj64
May 18, 2012.
Pcm is an exchange unit

Tiny
Hmac300
May 18, 2012.
I can get a PCM from another 97 lesabre that has 96,000 miles on it, just wondering if there is a chip behind that plate or if it will start if I just put another PCM in.

Tiny
Pcdj64
May 18, 2012.

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