Anonymous asked in Cars & TransportationMaintenance & Repairs · 9 years ago

1994 Firebird running rough NO Check engine light?

i have a 1994 pontiac firebird with the 3.4 liter v6 and 5 speed manual tranny. it started running rough a few days ago drove home and then tried to start it an hour later and woulndt start but cranked and cranked but no fire, it will only fire if i hold the gas pedal to the floor. i let it set over night and started perfect in the morning no problems, ran it for 10 mins and turned off and tried to start again and did the same thing cranked and cranked but no fire. im assuming it was a fuel issue possibly, replaced fuel pressure regulator didnt fix has a new fuel filter on it and the catalytic converter is gutted. took it to work and hooked it up to scan tool and all sensors are reading properly tps and map sensor, recently replaced tps sensor for low voltage. scan tool states quad driver 1,2, and 4 are bad but quad driver 3 is okay. got another pcm and now only quad driver 1 and 4 are bad, but now speedometer doesnt work so i got a bad pcm possibly? Alldata states to take out the knock sensor module out of the pcm to put in the new pcm in pcm replacement procedure but old pcm doesnt have one but my new one does? yes there is a knock sensor module in the computer im not referring to the knock sensor on the engine block. any idea wht my issue is? any help is greatly appreciated thanks everyone


the reason the catalytic converter was gutted because its the original cat and was falling to pieces and was becoming dust. the gutted cat will have no effect on the 02 sensors because they are on the manifolds and there isnt any beyond the cat

1 Answer

  • 9 years ago
    Favorite Answer

    Gutting your converter was a BAD idea. Your O2 sensors do not LIKE this and will give BAD readings to your CPU. CHANCES are that your THROTTLE BODY and IAC valve are clogged up and NOT responding to computer signals. REALIZE that on a FUEL INJECTED car, your "GAS"pedal is really your "AIR"pedal. Your foot only opens the throttle body door to allow AIR into the engine. Fuel is injected by signals from engine sensors and computations made by your CPU! The IAC valve FINE TUNES your fuel mixture and ADDS air when the computer TELLS it to. If it is CLOGGE up with engine sludge, it CANNOT respond. Try CLEANING the IAC (idle air control) valve with SEA FOAM and GUMOUT spray FIRST. ANy quicky lube can do this for you for $20 or so. Make SURE it is SHOWROOM clean for it to do it's JOB. Most converters and O2 sensors go BAD because this IAC valve is NOT doing it's job. Most CONVERTERS do NOT really need replacing at ALL!! GOOD LUCK!!

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