First, I did do a search and did replace the things you all suggested: O2's, MAF, MAP, Crank position sensor, Fuel Pump, Fuel Filter, ICM, Coil, checked for vacuum leaks, Sent the computer in for re-tune.

So, here is the problem. Most of the time the car runs great but every once in a while it will just start running real rich so much so that when you stop at a light, you can smell the gas in the exhaust and the car runs like it lost a cylinder. Sometimes you will be driving on the interstate and all of a sudden, you can feel the change in performance and hear the change in the rumble from the exhasut. After a few miles, it will change back and start running strong again. Sometimes, it will start out running rich and change after a few miles. When this is going on, the car does not misfire, hesitate or stumble throughout the RPM range.

We all know, F-Body drivers are "SMARTEST ON THE PLANET" so I know one of you has the fix for this. WHAT IS IT?
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Yellow Green 96' z28, M6, LT4 Hot Cam, 58mm BBK TB with bypass, Pro Mag 1.6RR, Comp’s Hardened pushrods, Comp’s HE Lifters with LT4 Springs, Extreme duty timing set, Pacesetter Headers, Flowmaster cat-back/no Cats & 3” pipe, K&N CAI, 160 Stat, Vortech Elbow, March pulleys, LT4 KM, B&M ripper, NGK TR55's, MSD Blaster coil, BMR STB, Walpro 255, 4.10’s, PCMFORLESS tune.

 

This is the kind of problem that can sometimes be tracked down with a continuous data scan/log using something like AutoTap.

 

Hi Injuneer,
This is the same problem I have had since last year. I have Autotap and have run several logs. Last summer I sent you some to look at for me and you were not able to identify anything with the data I sent. I have since changed cams, lifters, timing set, all gaskets, FPR and the problem still exists.

 

My 96 has the same problem. I have used auto tap on it and have not found any thing to be wrong. Just starts running like crap for a few miles then goes back to normal.

 

I am determined to find and fix this problem so if anyone has any input of any kind, let me have it. I'm sure the car did not come equipped with this problem so there has to be a fix for it.

F-Body drivers are: SMARTEST ON THE PLANET so Never drive faster than your guardian angel can fly.
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Yellow Green 96' z28, M6, LT4 Hot Cam, 58mm BBK TB with bypass, Pro Mag 1.6RR, Comp’s Hardened pushrods, Comp’s HE Lifters with LT4 Springs, Extreme duty timing set, Pacesetter Headers, Flowmaster cat-back/no Cats & 3” pipe, K&N CAI, 160 Stat, Vortech Elbow, March pulleys, LT4 KM, B&M ripper, NGK TR55's, MSD Blaster coil, BMR STB, Walpro 255, 4.10’s, PCMFORLESS tune.