Greetings. This is my first post so please, be gentle. I have a 92 Z28 with a 305 - I always wanted one of these cars when I was younger... Did I mention it's red. Anyways, I seem to be having some bad luck with her lately. Most recently she has been acting up after driving her around town for about half an hour - no symptoms when she is cold. When it gets hot, the idle goes up and down, often killing the engine. She does, however start right back up. When this happens while driving it gets interesting. Under no acceleration, she often dies and I lose power steering etc. Under heavy acceleration, she bogs down. I almost have to keep pumping the gas pedal to keep her driving. Anyways, we limped down to the shop where the guys immediately told me it was the Throttle Position Sensor. $80 for the part and an hour of labor later, she is still doing the same thing. I plan on taking her back to the shop tomorrw, but I can't really afford to pay someone else, especially if they are not able to fix my problem. I am not a mechanic but I have done a few things myself including the heater core in this car. Being that I am in school full-time and work I don't really have a whole lot of time to play around in the dark. If this is something that is obvious/ easy to diagnose and repair then I am willing/ able to do the work myself. If anyone has any ideas as to what may be causing my problem, then I would really appreciate the response. Thank you in advance!

 

Hello 305, I am trc88irocz and I just fixed my '91 Z28, i was having the same problem with my car. Turns out it was the fuel injectors. I changed the TPS,IAC valve,coolant temp sensor,wires,spark plugs,module, cap and rotor,coil, intake gaskets, plenum gaskets,runners gaskets, even gaskets on the throttle body, O2 sensor, I even removed the catalytic converters and replaced all the vacuum hoses, none of that stuff made any differrence, it would still SURGE up and down and run like crap! I was gonna replace the pressure regulator next, but a friend had a set (8) of injectors he said I could try. I did and my car runs GREAT! no surging. hooray! I say try the injectors and go from there. As old as your car is it probably wouldn't hurt. BTW my friends injectors came from a '95 LT1 camaro. I hope this Helps you.

 

Is your car TBI? Throttle body injected? My 305 does the exact same thing as well. Makes me mad!!! Albeit my car is an '88 with a TBI unit on top. Trc88irocz might be right here, I have replaced most of the things he has as well, and to no avail. If it is a TBI engine there are no injectors to change. Correct me if I'm wrong guys, but you might have to change the entire TBI unit.

 

Thanks trc88irocz. I wouldn't have thought of the injectors but it is definitely possible. As you said, it couldn't hurt. They may be original. My car has TPI so I have 8 injectors... this could get expensive. I plan on trying a few things this weekend to see if I can diagnose the problem.

 

Well... I didn't get a chance to work on my car this weekend so Im still wondering what is wrong with it. It is strange to me that it only surges when it reaches operating temperature. Not only that, but it only happens after I turn the car off and back on after driving around for about a half an hour. Perplexing.

 

Check your maf sensor, my iroc does the same thing, i unplugged my maf and it was still idleing wierd, went to advanced auto and picked up a new one, plugged it in and 100% turn around. hope it helps.