IronEagle455

Hi, Iīm having issues with my 91 Firebird 305 TBI and thought maybe some of you guys could help me out.

I just bought the car, it has 108k miles and sat for a LONG period of time before I got it, I vacuumed about 3 pounds of dirt just from the engine bay.

When I first got the car, it would not idle at all, the car would fire right away and die as soon as you let go of the accelerator pedal, it revved quite good thou.

I replaced plugs, wires, cap and rotor, not much change, then I did some research and found maybe my CTS was bad, so I replaced it along with installing a thermostat(car came without one), the car idled rough, but at least it didnīt die on me anymore.

That night I let the car idle for about 30 minutes and then, stalled, the car wouldnīt crank again, turns out I needed an alternator(gauge panel wasnīt working at the time), installed a new alternator and car fired right up, rough idle, but not as rough.

The car has no exhaust as someone stole it from the previous owner, looked down and what do I see? O2 sensor is broken!, just bought a new one, havenīt installed it yet, cleaned up EGR, it moves freely and holds vacuum, checked vacuum lines, cleaned TPS(had a dead spider inside, how? IDK), took out IAC and cleaned it), after all this the car fired up and had a ROUGH idle, worst than before, my brother toyed with the TPS and we just tuned it off, then 5 minutes later I went back and turned the car on, it idled fine, for a minute, then it stalled again, disconnected EGR and tapped the vacuum hose and car fired and idled great, connected the EGR back and car fired good and ran better than ever, took the car around the block and had no problems, at that moment I thought everything was great, then I let the car cool down for 3 hours, went back and the rough Idle was back, disconnected the EGR once more and somehow helped, connected the EGR and again ran good.

Sorry for the LONG post but this is driving me crazy, can the O2 sensor be causing all this?

This is my first fuel injected car so please be patient!

RWO3

The PCM doesn't use the O2 sensor at all until the PCM enters "closed loop". Closed loop (opposed to open loop) is basically when the engine and O2 sensor are warm and will produce reliable information to the computer. The EGR valve should never be flowing at idle, but if there is a PCM malfunction and it is, it will cause a very rough idle if not cause the engine to stall.