I had been having trouble with my engine. '86 GT auto, daily driver. Whenever I would get to cruising speed, it would start to cut out. Never completely, just a little fluctuation in the speed. I could just feel it a little bit at first but it gradually got worse. I could see it on the tach, the needle would jump every time it hesitated. If I hit full throttle, it would accelerate normally with no fluctuation. So I hit the search button here, it was not an uncommon problem. The consensus seemed to be the EGR valve or something electrical. Well I tried a couple of things, checked the EGR valve, it was clean and seemed to be operating correctly. I had a spare TPS, coil, distributor and module. Tried replacing each of these to no avail. Still hesitated. Tried a new O2 sensor. Nope, not that. Probably could use a new one anyway. I had read that a lot of people with this problem fixed it by replacing the spark plug wires. It just didn't seem like wires to me. Every electrical, ignition problem I've ever had always got worse the faster you would go. Well, I replaced the wires following the suggestions here and the problem went away, finally! Just thought I'd drop a note here for anyone else searching for an answer to this problem. One more saying replace the wires first! 200500 on the odometer and running strong again.
