Hey guys, I just purchased a 99 GT and am having a problem. The car misses all the time at low rpms...anywhere from 1200-1800 rpms when you put any throttle into it. Then midrange rpms seem to be fine until you punch it. Then the car pulls hard but spiratically misses. It also misses very randomly in the mid rpm range with several throttle positions. Its not like the car falls flat on its face. just a quick miss. No codes are set, stored or pending. Already cleaned the maf sensor. Checked for vacuum leaks, none. O2 sensors are cycling properly. Changed fuel filter and did a fuel injection cleaning wtih BG commercial cleaner right through the fuel rail. Cleaned the throttle plate. Haven't checked plugs or coils yet becasue I figured if there was a badly worn one, it would happen constantly, and not just at low rpms or full throttle. Checked tps sensor, voltage readings are correct. and its not like theres a burnt contact on the sensor because it happens at all positions of the throttle. EGR valve is opening at proper times, and the IAC valve is opening correctly. (all checked with scan tool) Ok, now I reset the pcm after cleaning the maf sensor, and the car ran great. pulled hard, no misses at all. Then after driving I would say 100 miles (guess), it started to come back. slightly at first, but progressively getting worse.
I had a guy at work (technician) check out the scan tool data and he said it seemed to him that bank two is running slightly leaner than bank one. So I checked for leaks at the intake manifold, all vacuum hoses, and all gaskets with propane, no change in fuel trim or idle quality. Well I think thats all the info I have so far. I'm completely stumped. If anyone has some ideas or input, please share. Thanks for your time and help.
I had a guy at work (technician) check out the scan tool data and he said it seemed to him that bank two is running slightly leaner than bank one. So I checked for leaks at the intake manifold, all vacuum hoses, and all gaskets with propane, no change in fuel trim or idle quality. Well I think thats all the info I have so far. I'm completely stumped. If anyone has some ideas or input, please share. Thanks for your time and help.