Ok I have a 87 350 tpi, cam .580 lift .280-.288 duration @ .050" advertised, comp cams, HSR, 24 lbs injecters, cool air intake, 2300 stall. I am having problems at idle with the car in park or driving it. It backfires under a load at low rpm, over 2500 runs great. I have checked fuel pressure is about 32-34 psi ( I was told to run this pressure because of the oversized injecter) , I reset the IAC, checked the TPS, timing is correct, spark plug gap is good, need help. Also I have a AFR gauge, reads lean until RPM's are up, then reads rich until I let out of the gas then it reads lean again.

 

32-34 PSI? At high-idle?? If I remember correctly, my car is at 47-48PSI with 24# injectors. I would bump that fuel pressure up and see if it the problem goes away.

Just my 2 cents.

Hope this helps!

 

Have you had it dyno-tuned? You're WAY beyond the stock TPI programming at this point.

 

OK, I have adjusted the fuel pressure up to 46 psi and played with the timing a little more. Now the car runs alot better, but at wide open throttle it has a slight miss, and I just can't figure it out. I have played with the fuel pressure and timing, the tps is correct, installed a new heated o2 sensor, compression test is ok. I was told to check the injectors, but am not sure how to do that, they are new accel 24lbs injectors with maybe 1000 miles. I don't have anyone around Bremerton, Wa. that does a dyno-tune. Please help, anything would help.

 

I am still having a problem with the car missing under heavy load. I was wondering if maybe it could be my spark plug gap, I still run the factory setting of .035".