Mustang TFI

[TC Chris]

Tonight's project: installing a remote, heat-sinked location for the Mustang's "TFI" (thick-film ignition) module. The TFI is a known failure point for Fords of that era. Ford saved a couple pennies per car by locating it on the distributor, on top of the engine, a place where its subjected to high heat. And guess what high heat does to the TFI? They designed it to survive the warranty period. My first one failed in about 1995. The engine just stopped as I was driving. Well, last fall, last drive before storage for the winter, the engine stopped as I was driving. That time it restarted but it doesn't do much for confidence in the reliability of the vehicle. I ordered a relocation kit from Jason McCully. So tonight I was out drilling holes in my Mustang to mount the heat sink. Ouch. My 1960s vehicles have enough room under-hood to set up housekeeping or stretch out for a nap, but by 1986 things were getting crowded.

Next is to rotate the distributor to get access to the screws for the old TFI. The video says to mark it before rotating and then set it back to the mark. Seems like maybe it would be wise to check the timing. I've never timed the Mustang. It's electronic and stable. I have a couple good old timing lights from breaker point days, but wonder if they'll handle the higher ignition voltage of newer vehicles? Any experience, good or bad, with that?

I'll need to consult the shop manual for timing conditions. No vacuum advance line to plug on this one, and no mechanical centrifugal advance to worry about. Any experience with timing EEC-IV Fords?

Chris Campbell

[electra225]

My experience with Ford TFI and also the older Thunderbolt ignition has generally been good. The TFI that mounts on the distributor is probably the better of the two systems as far as reliability is concerned. Secondary ignition condition, plugs, plug wires, distributor cap and rotor are critical for long life and reliability in that system. The GM HEI system and the newer C3-I systems were almost bulletproof. I found it critical to use genuine Motorcraft igniton modules in the TFI systems. Not only do the aftermarket modules fail more often, they can also mess up other systems, such as injector "on times". If we were investigating a weird or intermittent driveability issue in a Ford with TFI and found an aftermarket ignition module, that was our first avenue of investigation. I kept a known-good Motorcraft TFI module in my tool box for substitution testing in such cases.

[TC Chris]

Apparently the good Motorcraft modules are unobtanium now. The current ones are not reliable, and the aftermarket brands are superior.

The problem was just poor design, putting the modules in a location where excessive heat kills them. There was a big lawsuit and that's where they discovered that Ford knew the devices would fail--shortly after warranty ended. It was a purely cost-related design decision.

Chris Campbell

[electra225]

The 5 litre Mustang guys ran high energy aftermarket ignition systems back in the day, I believe made by Mallory. I had one in the shop that had punched through the insulation of the stock plug wires. They had to run spendy wires made to handle the high voltage.