Car is a 1992 Camaro with a 305 engine and TBI. Engine starts OK when cold but has a very erratic idle (500-1500) and occasionally stalls. When I try to drive it it surges forward from a stop almost dies and repeats this routine until about 40 MPH. The idle smooths out a lot when warmed up and runs better but still studders a little when the gas is depressed. The vehicle has a new fuel filter. It also shows 17" of vacuum when warm. I spayed carb cleaner down from the top into the IAC opening with the engine running. The injectors look to be spraying OK and both about the same. I am at a loss of what to do to fix this problem.

 

Kaupca

You may have a weak fuel pump - not enough fuel pressure. When engine is cold it ECM commands richer fuel mixture. Once engine warms up, ECM will lean out fuel mixture. Stomping on gas paddle requires more fuel, which is not being delivered by tired old pump.

Rent a fuel pressure test kit - available in many quality auto parts stores. A stock TBI system likes to see 11 to 14 PSI of fuel pressure. There is no fuel pressure test port in TBI setup. You'll have to install a T either at inlet fuel line or next to a fuel filter.


//RF

 

I hate to ressurect a dead thread but my 92 Camaro RS recently started doing this same thing. When its cold the car runs really erraticly and will stall on take off, but after the engine warms up some it smooths out and will only stall out if you punch the gas really hard. I think the car has a fairly new fuel pump on it but every post I can find on problems like this end with someone suggesting to look at the fuel pump and the OP never replys if that was the problem or not.