I'm looking at a 93 gmc 1/2 ton pickup with the 305 tbi. He just changed out the cam and went through the engine but he says its running really rich. What could be the problem with it? Does the computer need to be reprogrammed or does it need a new 02 sensor? Any help would be greatly appreciated, thanks

 

Is it fuel injected?

I have a 93 GMC S15 Jimmy with a 4.3L Vortec, for about a year before the fuel injection system when kaput it ran really rich.

 

probably needs a computer reprograming,

even a mild cam can throw a MAP system like TBI uses way out of wack

I tune FI cars mainly TPI and even 1 step up from a stock cam can throw fuel and timing for a loop on MAP systems, MAF is alot more forgiving,

cause it uses vacuum to determin fuel and timing by putting a cam in esspecially 1 with high lift and duration will throw the ecm way off, the computer will think the engine is under more load then it really is and add fuel to compensate for it, even at an idle,

but a new O2 is always a good idea

 

I agree with 89vert. A TBI car will need some tuning after a cam swap. There are ways to do it without getting the ECM/PCM recalibrated but its not as effective.