Shuts off at red light

BOS1957

MEMBER
1992 PONTIAC GRAND PRIX
3.4L
V6
2WD
AUTOMATIC
146,000 MILES

Hey guys, this is BOS1957 the guy with the s10 fuel pump, have a new one for you. My buddy in Florida called me about his car listed above. He says it shuts off at the red light, but starts right back up only with the AC off. If he has it on no trouble. So he started to change thing with no avail. TPS, MAP, EGR, he found a bad gasket and the spring was stuck. Nope not it still same problem. Took it to MM&J they could not find anything and it has no codes! I told him it might be the computer, same problem. Now he tells me he changed the coil pack and module. No change. Then he told me this morning if he pulls off any spark plus wire it shuts off not skip. I never heard of anything like this. Have you?

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good evening.

Lots of guessing and no results.

The throttle body is the first stop. Make sure the plate is clear of all carbon. That will block the ports.

The idle air control on the throttle is what controls the idle. You need to remove it and clean out the passages. That would have been the first thing I would have replaced if I was looking at the car. The rest of the stuff that was replaced had no effect on the stalling.

Roy

REMOVAL:

1. Disconnect the IAC valve electrical connector.
2. Remove the IAC valve attaching screws.
3. Remove the IAC valve assembly.

CAUTION: On IAC valve that have been in service: DO NOT push or pull on the IAC valve pintle. The force required to move the pintle may damage the threads on the worm drive. Also, DO NOT soak the IAC valve in any liquid cleaner or solvent, as damage may result.

Cleaning and Inspection:
1. Clean the IAC valve O-ring sealing surface, pintle valve seat and air passage.
Use carburetor cleaner and a parts cleaning brush to remove carbon deposits. DO NOT use a cleaner that contains methyl ethyl ketone, an extremely strong solvent, and not necessary for this type of deposit.
Shiny deposits on the pintle or seat are normal, and do not indicate misalignment or a bent pintle shaft.
If the air passage has heavy deposits, remove the upper manifold assembly for complete cleaning.
2. Inspect the IAC valve O-ring for cuts, cracks or distortion. Replace if damaged.
3. If installing a new IAC valve, be sure to replace with an identical part. The IAC valve pintle shape and diameter are designed for the specific application.
4. Measure the distance "A" between the tip of the IAC valve pintle and the mounting flange.
If greater than 28 mm, use finger pressure to slowly retract the pintle. The force required to retract the pintle of a NEW valve will not cause damage to the valve.

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