- Feb 11, 2017
- 3
- 1
- 13
First a little about my car. It's a 1991 5.0 gt convertible 5 speed. Only upgrades is the explorer intake, explorer injectors, equal length headers, catless h pipe, and 3G alternator, all else is stock.
I have ran this configuration for years with no issues, but now I have a problem I can't seem to fix.
It started to run rough one day, idled fine, no backfire, between 2k-3500 rpm it misses. I did a tune up, all motorcraft parts, changed the fuel filter. Checked timing, still no change. What is odd is that if you unplug the alternator regulator it runs like a top.also the power accessories i.e. Top, windows and headlights make the problem worse. Once i plug it back in it goes right back to the miss. Alternator is putting out 14.5 volts. I had it checked by my local rebuilder and it tested good. I even swapped in a new one and same issue. I checked all wiring to the alternator and everything looks ok. I have literally been through this car. I have changed the tfi and distributor. Fuel pressure is good, stock regulator. I have traced wires looking for shorts. And have come up with nothing. I pulled the ecm, the caps were leaking a bit but since there was no board damage I replaced them and put it back in. I swapped in a good known maf, tps, and idle air with no change. Also there is no stereo equipment, msd, or other add ons that could be Causing this problem. Battery is good as well. I have cleaned all the grounds.
Any ideas would be greatly appreciated. I have owned this car for 18+ years, and this is the first time it has stumped me. Sorry if this is long winded. Thanks in advance!!!!
I have ran this configuration for years with no issues, but now I have a problem I can't seem to fix.
It started to run rough one day, idled fine, no backfire, between 2k-3500 rpm it misses. I did a tune up, all motorcraft parts, changed the fuel filter. Checked timing, still no change. What is odd is that if you unplug the alternator regulator it runs like a top.also the power accessories i.e. Top, windows and headlights make the problem worse. Once i plug it back in it goes right back to the miss. Alternator is putting out 14.5 volts. I had it checked by my local rebuilder and it tested good. I even swapped in a new one and same issue. I checked all wiring to the alternator and everything looks ok. I have literally been through this car. I have changed the tfi and distributor. Fuel pressure is good, stock regulator. I have traced wires looking for shorts. And have come up with nothing. I pulled the ecm, the caps were leaking a bit but since there was no board damage I replaced them and put it back in. I swapped in a good known maf, tps, and idle air with no change. Also there is no stereo equipment, msd, or other add ons that could be Causing this problem. Battery is good as well. I have cleaned all the grounds.
Any ideas would be greatly appreciated. I have owned this car for 18+ years, and this is the first time it has stumped me. Sorry if this is long winded. Thanks in advance!!!!