hi guys i am new to the tpi thing. bought a 91 z28 350 couple of weeks ago. it is giving problems idling it will run for a few minutes and then stall it will not start right back up acts as though its flooded hold it to floor and crank it over some and it will restart. also stall sometimes on a coast down to stop and there is hesitation when stepping back on the gas. i removed the TB and cleaned it and the IAC. that seemed to solve most of the probelm,until i repaced the manifolds with headers and removed the cats. now the problem is much worse. i would have thought changing the exhaust would make it leaner but it seems rich. the car also has an aftermarket chip but the previous owner had no info on it. same as the cam said it was 2 sizes over stock i dont have a scantool yet. i hoping someone could point in the right direction. thanks for any input ED

 

Welcome to third gen, mine had similar problems, I will try to help. mine ended up being many things, need some more info....did you reset the min. idle air? (after cleaning the TB and IAC housing) check the TPS voltage (.54V) as for the chip, what kind is it? Could be a simple (or not so simple to find) vacuum leak.

 

hi joe thanks for the reply. sorry it took so long to do the checks but i had to install a tach. i set min air using the procedure off this site. idle would not go below 700 also when i was waiting for the iac to extend i noticed it was making a clicking sound is this normal? set the idle as low as it would go, plugged the iac back in and it would barely idle then stalled, i could smell fuel and the motor was very hard to restart. once it was started idled at 1000 about the same as before. tested the tps .60 volts at idle 3.2 at wot i checked this several times the first time at wot the volts read 3.2 and thenfell off. i also checked for vacuum leaks using carb cleaner and propane nothing obvious found. i dont know what chip it is the label says off road use only. maybe its for a 4 wheel drive .let me know what you think,thanks ED

 

The IAC clicking is OK....TPS, should be .54v sitting still, and over 4.0v at WOT (with the voltage droping like you talked about the TPS is bad) Chip, get rid of what ever you have and get ahold of TPIparts.net, and get a AC Delco chip, and IAC...ohm out the injectors to see if you have a bad one. Also need to check your timeing (with the cam try 10* BTDC)

Let us know what you find,
joe