Flyingvman

92 firebird 5.0 TBI is running rough,rich and the idle goes hi and Low. There's hesitation vibration but no check engine light. What can be wrong with it. Seeking advice.

Schurkey

About two dozen things. Maybe more.

What does the data stream show on the scan tool? I'd be looking at IAC counts, commanded idle speed, actual idle speed, O2 crosscounts, short- and long-term fuel trim, coolant temperature and system voltage to start with.

What is the fuel pressure when the engine hesitates?

When was the last time this car got a proper tune-up including fuel filter, plugs, distributor cap and rotor, plug wires, air filter, PCV filter, PCV valve, charcoal canister filter (if used) and a compression test?

Have you ever cleaned the throttle body with aerosol solvent?

Does this have an AIR pump? If so, does the diverter valve work to switch air from upstream to downstream?

Flyingvman

Very strange this bird has been. First it was running rough with lots of vibration and jumping 5th gear to neutral. The weather was warm and no rain . Now that it's cold and raining the bird is running fine . I'm thinking it's a vacuum leak of some sort. If the weather permits I'm still going to give her a minor tune up and check all vacuum lines. I thought that the check engine bulb could be fried so I unplugged a sensor and the light went on. Very strange this bird . Ty for replying.

Flyingvman

I recently bought this bird about three months ago and I've done nothing but a oil change. She actually has been good till just recently. Im going to check the IACV, cooling temp sensor, egr, etc. ect.