DeanK

Have 1990 XLT 4x4 with 5.0 liter in it with AOD transmission. Truck starts fine idles fine can see small miss when at idle. Truck drives fine around town, but once on highway or anywhere speed is above 45mph truck develops a miss and even with pedal to floor will not go over 70 on highway (this is in overdrive) place tranmission in D miss is more pronounced and truck has seems more power. This motor was installed a little over a year ago and has run fine with no problems. Had new front fuel tank installed a year ago, fuel filter was changed then. not sure if ejector problem or ignition related. Has anyone had this issue before?

DeanK

Ok think I've figured this one out. Like I stated truck would start fine, drive fine until it warmed up good then would start missing thing. After checking fuel pump and ejectors and found no problem decided had to be electrical. Changed coil and man what a difference. Truck ran like brand new, til yesterday then miss came back and then went away after a couple of miles and did same thing again. So last night after it got dark went outside and started truck and man what a light show. All wires had spark jumping off of them, they are less then a year old . even around new coil had spark going to ground. Was not raining or even damp last night. Going to get new wire set today and I guess replace new coil, ordered this one from Rock Auto, will try to figure out which one to go with but I believe this is my problem.

raski

I believe you found the problem. Some aftermarket wires are junk. I would stick with Motorcraft when it comes to ignition and I would replace the plugs,cap and rotor too. I thought I once read about a TSB regarding proper routing of the wires which you may want to look into.