91 fox

I have a 91 GT w/5.0 that when you step on the gas it's like it chugs/ stumbles. I checked codes the only thing it came up with was 12. I have put in new plugs, wires, cap, rotor, blaster coil, fuel filter, checked timing(12 degree) run Seafoam, octane booster threw a few tanks, cleaned mass air flow, cleaned idle valve, Car had been sitting for a while before I bought it. The car has BBK headers, Trick Flow upper & lower intake manifold, X pipe. The guy I bought it from did the work on it him self, said it needed fine tuned. Is there anyway that he could have mixed up the wires on the injectors?

All help would be appreciated
Thanks

mattdel

The injector harness is pretty straight forward, they are only just long enough to reach their specific cylinder. You'd have to extend the harness to get it to reach the wrong one.

I'd check to verify you have the correct firing order on the cap.

91 fox

I have done that 3 times order is correct, I even put cylinder at TDC and check dist position.

mattdel

Check fuel pressure at idle and WOT. Idle should be steady at 33psi, WOT at 40psi.

Bubba 95SN

Remove spout when timing? Try cylinder balance test?

enix187

Is your baffle in your fuel tank loose and rattling? go to the back of the car and shake it left and right (not up and down) and it should be quite, if its loose it will be loud, really LOUD

livinitup11

I had similar issue years ago when i was new to my Mustang and before i did any work to it. It would drive ok for about 15 min then start chugging and bucking the more i stepped on the gas. So after several hundred dollars with different shops trying to diagnosis my car and still not fixed I figured i would just start changing parts. While changing out the Fuel pump i noticed the fuel screen sock had fine material trapped in it so when i would drive the car for a little while the material would clog the fuel pump screen and after shutting the car off it would settle back down into the fuel pump screen sock. Dont know if thats your problem but thats what fixed mine. Good luck!!