amcnellis

The car in question is a 1991 Chevy Camaro RS with 305 TBI. After driving the car 30km or so, while the engine is still warm I am getting a low, rough idle when starting the car, lately it has actually been stalling out. I can usually get it to start again just by turning the key. If I start the vehicle again, and push the rpm to over 1000 for about 10 seconds, the car will go into gear without stalling, but acceleration is rough for the first couple KM until everything is warmed up, and the idle is very low and shaky. I recently replaced the O2 sensor because my fuel mixture was running thin, since the replacement the rough idle on acceleration has lessened, but it is stalling out , while in park more frequently.

Also it may be worth noting (or just make me sound like an idiot for mentioning) that if I release the pressure from the gas tank before starting the car, it won’t start. Any input, comments or suggestions would be greatly appreciated.

bigal55

iTrader: (1)

What is your fuel pressure? The reason I ask is because you stated that if you release the pressure from the tank, the car will not start. Your fuel pump should be capable of providing 15 psi fuel pressure regardless if the gas cap is on or off. You also stated you changed the O2 sensor because your fuel mixture was running "thin". Does that mean your mixture was lean? Again pointing to fuel starvation. Fuel filter plugged? Kinked or obstructed fuel line? Bad pump? Check your fuel pressure.

Ghettobird52

Incorrect; the TBI motor should give 12PSI

And also there is no 'stock' Schrader Valve to check pressure, he can install one like most of us though.

Schurkey

Consider the difference between what the pump will provide, versus what the fuel pressure regulator is set at. The pump probably can produce 15+ psi, (at no-or-low volume, especially) but the fuel pressure regulator is going to be set for the typical 9-to-13 psi as spec'd by GM.

If that engine is run hard, the fuel pressure should still be at regulated pressure--but with a defective pump, poor electrical supply to the pump, or partially-plugged fuel filter, pressure can sag. Given a bad enough pump or pump wiring, the pressure can sag with little or no load on the engine.

Yes, testing fuel pressure sounds like a good idea on this vehicle.

ex-x-fire

You could have a bad egr control solenoid or a sticky egr valve. Try plugging off the egr vacuum hose & driving it for a couple days.

morgsie

iTrader: (1)

plugging the vac line wont do anything if the valve isnt seating correctly or if the diaphram is damaged. remove egr and inspect valve, it will probably be full of crud. use vac pump and see if diaphram will hold vac for any length of time. pending results replace or put a block off plate on. egr solenoid can be tested with vac pump and 12v.

Ghettobird52

I would be mind blown shock to see a TBI come up at 15psi, majority are lucky to even pull 12-13psi. While the most are usually 11