Car racing when started

ED56

MEMBER
1990 BUICK REGAL
3.1L
V6
2WD
AUTOMATIC
60,125 MILES

This car ran perfectly until a month ago then started racing and stalling. I have replaced the IAC three times all AC Delco from Rock the TPS twice also AC Delco and the temperature sensor IAC some times gives erratic readings but no service engine light or code shows. I then put it in learning mode and worked for about 12 hours then right back to the same problem. Replaced the ECU twice first one was bad same results checked the fuel pressure was low changed the fuel regulator the fuel pump and the fuel filter. Now right on 40 PSI and holds it. Checked for vacuum leaks found none. Sent it to two shops no luck. I know I am missing something hoping someone has a clue. I am a certified Marine Mechanic but this has me lost.

Thursday, July 18th, 2019 AT 11:23 AM

1 Reply

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

This sounds like a vacuum leak somewhere. Could you please double check the intake manifold, especially the inside that runs along the engine valley. A good way to check is to get a propane torch and barely crack it open, so that just the propane is coming out. Keep it unlit. Start your vehicle and let it idle. Run the torch along where you want to test. When it passes a leak, the engine will rev up as the engine ingests the propane. Please try this and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros

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Friday, July 19th, 2019 AT 12:08 AM