I am on my sixth Camaro now and my fourth thirdgen. I've had this 91 for a week now and am trying to get it all straightened out. First off, it is an LO3 that is pretty much stock. It gets about 8 or less miles per gallon combined city/freeway. The car has new plugs (bosch supers), wires, MSD coil, air filter, CTS, ignition control module, radiator and cap, alternator, water pump, cleaned IAC, new EGR and has a fresh oil change. When I got the car it ran really poorly, after replacing most of what I listed above, it runs a tad better. The initial timing was at 2 degrees retarded and I moved it to 1 degree advanced (wish the ESC unplugged).
What I notice most about the car is that when I drive it at part throttle it has a heavy miss throughout the rpm range and it is worst down low. When I give it moderate gas or even go to WOT it seems to clear up. I even get a little sideways into second as the shift kit kicks the posi out hard. The idle when cold is at 750-800 rpm and when it warms up it gets drops to 500 rpm and has a slight lope to it. The car seems to heat up relatively quickly, and if it is driven and left to idle it will get to the red zone which is where the fan kicks on and drops the temperature. I checked for vacuum leaks and couldn't find any, and I assume that I have good fuel pressure because I am overfueling. My o2 sensor appears to be newish, and I am going to pull it to inspect. If anyone has any idea of where to look or what to check, I would greatly appreciate it. Thanks in advance-

 

Have you checked the TPS? Check your fuel pressure, maybe the previous owner messed with the fuel pressure regulator. Have you checked the fuel filter, catalytic converter?

 

I have not checked the fuel filter or the TPS. The fuel pressure is something I am going to check next. I was working on the car this afternoon and found out that the car has a hypertech thermo(master?) chip. The car also has a 160 thermostat which I figure is for the chip. I put some premium gas in the car today and I noticed that some of the hesitation cleared up, but it wasn't fixed. I don't have a factory chip, and I am looking to get one and see if it clears up my problems. Also, I checked the timing yesterday and I noticed the timing mark bounced around (est unplugged) from 0 to 4 degrees advanced. As if my problem was limited to this, i've had some serious overheating issues. Everything has been replaced, heater core, wp, hoses, thermostat, CTS, coolant. It is driving me nuts!

 

hmm, well i would def. replace the thermostat with a 180, 160 is too low and i would replace the chip with a stock one. I have a stock chip for a 1991 LO3 if u want it. whle you checking your fuel pressure, i would go ahead and clean up the throttle body and either check or replace all the gaskets, you can get a rebuild kit for cheap for tbi's. Do u have the cable to datalog, if so it would be a good idea to check your numbers, it might be a good indicator where you problem is. Good luck with it, its a pain in the ****, i went through a similiar issue and it took a long time to solve it.