Misfire Issue

[hatchback88]

I've got a 89 fox that ran great in September 2011. It was down for a year do to a torque box issue but I have now got it back together and running again it hasn't been fired up sense Feb of this year. So I pulled my equal lengths off and put long tubes on. Fired it up and it ran great. Next day replaced the plugs and started it up and I had a miss on accel possibly at idle but can't really tell due to the cam. Found the msd wires and cap cracked and corroded replaced all of it. Fired up today no miss on accel ran great until it was up to operating temperature now I've got a bad shake/miss on deceleration. Not sure if its something as simple as plug gap or what but before these plugs l had e3 s in it and no problems let me know what you think

 

[jrichker]

The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

View attachment 144308

See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton
diagram courtesy of Tmoss & Stang&2Birds

 

[gearheadboy]

I've had that issue after I dropped a plug on the floor and then installed it. Sometimes a crack in the plug will make them miss when warm.