Sorry for the long post but hope someone can help. I have a '90 Auto 5.0 TPI with a stall/surge problem. The car sat in a barn for 2-3 years but has been out for about a year now. Car starts fine but after 5-10 minutes driving, will surge and idle will go really low and stall. Seems to do it mostly at stop signs, lights and on hills. Weirdly, when the A/C is on - the stalling goes away. Of course as soon as I turn the A/C off, the stalling comes back.

My mechanic did a tune-up, replaced the IAC, fuel pump (he had to replace the sender) and replaced the fuel injectors with these: http://www.fiveomotorsport.com/Injec...sTPI.asp#caddy
And after all that, it's still stalling. The car is bone stock except for a Flowmaster but I've noticed the exhaust does smell bad.

My mechanic just replaced the distributor a few weeks ago with a rebuilt Cardone from Auto Zone. The distributor replace made sense to me since he said the A/C generates a charge which raises the idle and why the car doesn't stall w/the AC on. But even after replacing the distributor, it's still stalling/surging. My mechanic is about out of ideas and he said there are no vacuum leaks. He now thinks it could be service bulletin #91-239-6E Low Speed Drivability (PROM) New Knock Sensor Available (Feb. 28, 1991) and that I need to replace the PROM with #16163139.

Does anyone know if this PROM chip update fixed a stalling problem? I'll take any advice and appeciate the help.

 

Check your coolant temperature sensor and wiring could be the problem. should be black and yellow wires..