Hi everyone, I'm having some trouble with my camaro's you system. I'm not a very experienced mechanic, more of a parts changer at this point and I was hoping somebody could point me in the right direction.

Last year I had trouble with the car running poorly when warm, it would cut power and die unless it had half throttle or more, but would still cut power under a load as if I was on and off the gas. To solve this I changed:
Plugs (Accel)
Wires (Accel)
ICM (Accel)
Coil (Accel)
Cap & Rotor (AC Delco)
O2 sensor (AC Delco)
Temperature sensor
Cleaned throttle body and intake

Now the car will run and stay running and holds constant RPMs at idle and under throttle, but it misses pretty badly and feels like it has less power. The motor is a bone stock 305 tpi with 127K, only modifications to the car mechanically are smog delete and a 3" flowmaster with no cats.
Miss is most noticable at idle, but i think it's doing it under a load too. I was told that the air fuel mix is controlled by the temp and O2 sensors on the early tuned ports, so I'm not really sure what to try next. Any ideas or words of advice? Thanks for reading and any responses!

 

Do you have a check engine light on? Have you check the ECM for codes?

I believe early TPI system had a MAF sensor but later had them tuned out because there was such a high failure rate on them. There are a lot of things that can cause a miss.

 

I had a full scan done on the car and everything is fine ECU wise, car is running around 195 degrees, only check engine code is a speed sensor. I'm leaning towards the issue being the injectors because whenever I run it with Injector cleaner the miss gets much better. It's still there, but much less noticable and less frequent.

 

I had this experience once with a '85 Z TPI and I bought Accel 21# injectors, a jar of petro jelly, and swapped out injectors. and ran fine.
Buy a Haynes manual for your own good.

 

I already have one and it's helped me a lot, I'm pretty new to tpis, as my dad and anyone else that I would generally ask for help are strictly carburetor guys. Just curious, did you have any other modifications done? Just because I've heard that bigger injectors aren't really necessary unless more power is being made and the LB9s had 19# stock. Thanks for your help!

 

Yes, I found the same with OE 19# injectors, but the 21# made no difference as ECM controls the injector open time with the O2 sensor readings and adjusts accordingly.
No other mods were done. Two pound difference isn't hurting anything.
Change fuel filter, never hurts.


You're welcome.