sdconley78

I have a 91 mustang with the 302 block. I have put new heads, cam, intake, injectors, throttle body and distributor, coil and so on.
After the build the car ran excellent for a while. Very good response and pull on acceleration. Now when heavy accelerating the rpm hand shakes and it almost sounds like it is sputtering. It is still fast but nothing like it was.
I have changed out the distributor and the plugs and even gone as far as pulling the entire intake back off and redoing all the gaskets to make sure of any leaks. I changed the maf to make sure it wasnt a bad one and changed out the icm as well. Any help with this would be tremendous!! Could it possibly be a wiring issue and if so where would i start looking?

mattdel

The tach is a good symptom, but don't focus on it. The engine is struggling to breathe, it sounds like. Still got stock catalytic converters?

sdconley78

No convertors on it...
Ive even readjusted the valves just in case that was the problem..
Do you think i could have a bad ground. Maybe the ground that goes to the backside of the driver head from the harness..?
The bad thing is I know the power this car has and its not touching it right now. Ive even gone as far as putting another computer on it . Nothing...
Every sensor under the hood has been changed and checked. Nothing...
So frustrating. When accelerating hard it should pull real hard. But instead it feels like its choking out. Maybe not enough fire or something. I have even put another fuel pump and adj. fuel press. reg.
I was running low 12s and high 11s before this and i know as she sits i wont even attempt the track before she's fixed.

mattdel

Check compression?

wydopnthrtl

Once upon a time.. and on a different brand of vehicle I had a similar problem. It turned out to be the ignition module. On our 5.0L its a rectangular box on the side of the distributor.

sdconley78

Ok. I have been checking the wiring from the icm.. Is the wire for the ignition ground supposed to show ground when the ignition is on?? Because it's not when I check it.

sdconley78

Ok. I have an update. I checked all my wires. Even went as far changing a couple out that were in not so good shape. I wired in a new pigtail to the coil and the fluttering on the RPMs went away. But the studdering at high revs was still there and the check engine light came on. I ran the codes and there wee several. One was for my tps. I didn't think that was bad setting as how my throttle body was new!!!! And it came with a new tps on it!!! Well obviously it was bad. I changed it out with my old one and now the problem is gone!!! I had no clue that little thing could cause my car to run like hell!! But thank you guys for your input. Oh yea and of anyone needs any wiring diagrams for their mustang, I gabber them all now!!!