2.9L TFI Weird Issue


BoomTexan

Forum Member

Joined
Jul 7, 2025
Messages
34
Points
101
City
Atlanta
Vehicle Year
1986
Transmission
Automatic
Hey yall, I've had TFI problems for a little bit. Did the heat sink + dummy unit mod recently and it seemed to work fine for a little bit, but I've started having the problems again as it gets hotter in summer and I'm stuck in Atlanta traffic. To be expected and all that, I'm planning to relocate the TFI inside the cab close to the ECM, should be cooler inside.

Weirdly enough though, I've been carrying a 2nd TFI in case of emergency. It went out on me on the way back from church today, and I was prepped and ready. Hotswapped (pun intended) the 2nd TFI and it had the exact same issue. Curious about this, as the 2nd TFI should have immediately fixed the issue, right? Came back after it cooled down 2 hours later and it was fine again, working with both TFIs. Is this an issue with the ECM getting hot, or not resetting? It is located next to the blower motor, which has the door stuck open, so the heater core is always on and always blowing hot air.

Very very confused why this issue might be arising. After I replaced my water pump, it's running cool-ish, doesn't go above midway on the meter, so it should be less of a problem now, but it's still showing up. Any idea from yall on why that might have happened? I'm fine with getting a new ECM, but don't want to unload the parts cannon quite yet.
 
Coils also fail when hot....so do pickups in distributors. I doubt the TFI is your issue
 
Coils also fail when hot....so do pickups in distributors. I doubt the TFI is your issue
Ah, that would make sense. Just replaced my ignition coil with a new Delphi unit so I really doubt it's that, but I can carry the old one around and if the problem reappears I'll try and change it out and see what happens. Seems like something that I'll have to simulate to be able to diagnose.

Really hope that it's not the distributor pickup but we will see. Seems like a pain to replace the pickup, but thankfully I've got ~1 month between college ending and starting my job, so I can take the time to take the valve covers and intake off and do some work that I otherwise wouldn't do.

I really need a Honda or something, daily-ing 2 project cars is such a pain in the ass sometimes.
 
Ah, that would make sense. Just replaced my ignition coil with a new Delphi unit so I really doubt it's that, but I can carry the old one around and if the problem reappears I'll try and change it out and see what happens. Seems like something that I'll have to simulate to be able to diagnose.

Really hope that it's not the distributor pickup but we will see. Seems like a pain to replace the pickup, but thankfully I've got ~1 month between college ending and starting my job, so I can take the time to take the valve covers and intake off and do some work that I otherwise wouldn't do.

I really need a Honda or something, daily-ing 2 project cars is such a pain in the ass sometimes.
Never mind, I don't have a bearing press/puller so I will be purchasing a new distributor.

Not having a garage is such a pain in the ass sometimes.
 

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