Electrical Issue--tfi?? Ignition??

1992MustangGT · Nov 12, 2016

I have a 92 Mustang GT 5.0 and I've been having a random issue where I'm driving down the road and all of a sudden it just turns off, kind of like someone turned the ignition switch off. It will usually turn right back on by itself within 5 seconds, give or take. This morning I was driving on the highway and the radio cut out (shut off) for a half a second then came right back on; it did this twice. Then a half a minute later, the car shut off for about 2 seconds then came right back on.

I'm pretty positive it's an electrical issue somewhere, but my question is where? Is this possibly the TFI that's mounted on the front of the distributor? Is it something inside the distributor cap? Is this an ignition switch issue? Starter solenoid?? I'm not sure where to start diagnosing or how to diagnose whichever part is in question. In other words, if the TFI is going bad, is there a way to test it before spending the money on a new one just to find out that wasn't the problem? Any help is appreciated. Thanks...

5.0ttops87 · Nov 12, 2016

Mine would shut off because the ignition coil wire was too short and the engine would torque and pull it just enough off the coil. I'm guessing you'd see this, but just a thought.. or maybe your little ground wire that runs along that harness next to the headers or lower intake ?

mikestang63 · Nov 12, 2016

run the codes. sounds like a bad TFI

Blown88GT · Nov 12, 2016

1992MustangGT said:
...Is this an ignition switch issue?...

This.

1992MustangGT · Nov 12, 2016

Thanks for the advice. I will check all of this. Running the codes sounds like the best place to start. Will hopefully do this tomorrow if time and weather allows.

jrichker · Nov 13, 2016

When the radio cut off and the engine quit running was a clue that the ignition switch is going bad.

Recall on Ford Ignition switches:

Revised 7-June-2014 to add Torx bit picture and source. Also added replacement ignition switch wiring pigtail picture, part numbers and sources.

Some of the symptoms of ignition switch problems are things that don’t work or are intermittent like radio, turn signals, wipers or heater.

There was a FREE recall on Ford ignition switches. They overheat and sometimes catch fire. That burns up the steering column and sometimes the car interior. Since this is very old information, you may not be able to get the switch replaced for free anymore. The auto parts stores sell the switches for $13-$15.

While you are working on the switch, check the wiring and connector closely. A replacement connector with new wiring pigtails is available from most auto parts stores

AutoZone and Advanced Auto Parts have the same Part Number: 434 - may have to order, not always in stock

Advanced Auto Parts alternate part number: PT5534

Saleen0679 was nice enough to dig this up for us awhile back: Replace a 1979-1993 Ignition Switch Assembly

Torx bit set from Advance Auto Parts

Autocraft torx bit set – have small hole in tip for tamper proof screws.
Part No. AC571/W1386 Cost approx. $12 +tax

Diagrams courtesy of Tmoss & Stang&2birds

Ignition switch wiring

Fuel, alternator, A/C and ignition wiring

89gtsleeper · Nov 21, 2016

I agree on looking at the ignition switch and its connector/harness. The radio going out is the thing that makes me think not hecessa it the TFI. When the TFI issue happens, you usually won't be able to start your car back up until it cools down. Feel the TFI after a normal drive? Is it scorching hot to the touch? You can remove it and have it tested at the parts store for free. But the ignition switch is cheap, available online, and installs in about 15 minutes. You can at least take a look at your switch to see if there is any cracking or loose wires.

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Electrical Issue--tfi?? Ignition??

1992MustangGT

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