Dies suddenly and restarts immediately

[kaspr]

2002 LeSabre

Dies suddenly (usually or always at idle -- not 100% sure) and always restarts immediately. Not the fuel system - fuel pressure good, pump replaced. Already replaced the Idle air control (IAC) valve. Recent tune-up. No DTC codes. Should I suspect the crank sensor, or would that throw a trouble code? What else could cause this -- PCM?

Thank you.

[Tech II]

Check throttle plate and bore, for gumming up......

Check vac line to f/p regulator....

Could be a wiring problem.....start pulling harnesses while engine is running...

With crank sensors, when they fail, they don't usually restart right away.....

Also possible MAF problem.....

[Blue Bowtie]

The fact that is restarts immediately when the episode occurs will make diagnosis difficult.

The PCM will usually report an intermittent signal from the CKP or CMP and at least set a pending DTC. Also, as Tech II advised, those are inductive sensors and they like to cool down a bit before generating a signal again. Thus, they wouldn't be my first guess as causes.

Further, the MAF might also be involved, but the PCM has a very low tolerance for MAF errors. If the MAF signal goes out of range for as little as 600mS, the PCM will set a DTC. That would also tend to point me in a different diagnostic direction initially.

Inspect the electrical connector for the IAC for corrosion or damage.

Another thing to remember is that the ignition control module (ICM) is beneath the coil packs and provides ground for them. Since the ICM surface is aluminum and can corrode after a decade or two, it may be worthwhile to remove the coil packs and inspect the ICM connections, surfaces, and clean/polish as necessary. While this wouldn't necessarily happen only at idle, it is one other item to check and verify since it is not uncommon.

FWIW, I recently went through this on a GM van and the problem was the fuel pump power supply. Just for argument's sake, exchange the FP relay with an identical relay in the UEC, such as the horn relay. Inspect the FP relay socket contacts for discoloration or damage while the relay is out - That was the problem on the van I serviced.

[kaspr]

I checked all of these suggestions, and nothing is turning up.

When the engine dies, it seems like it is always with the engine at idle, and it does not sputter, but rather immediately quits with no warning, which tells me it's not a fuel delivery issue, but rather electrical. Either the spark is stopping or the injectors aren't pulsing, to cause an immediate kill.

It seems like the car conks out in three different situations:
1. when idling in Park or in Drive
2. immediately after starting (it fires right up but then sometimes will immediately kill)
3. when decelerating, with engine at idle

There has been no rough idling.

Let me know if you think of anything else. Thank you.

[kaspr]

I found the problem. The fuel pressure regulator was intermittently (once in a while) leaking spurts of fuel into the vacuum line. When this would happen, if the engine was at idle, it would kill. I actually checked for this at the beginning, but there was no fuel leaking at the time I checked it. I don't understand how a component as simple as a fuel pressure regulator can have times when it leaks and times when it doesn't leak. I'm thankful it's solved, though.