Engine dies after reaching operating temperature

1989 Ford F250 has rebuilt engine and was working fine for 2 months. Now the engine is dying after warming up. When it is cold, it starts up with no problem. The hand held emission system checker is reporting no problems, it is reporting system pass. Does anyone have any ideas?

Thank you, colby

If the ignition module is the orginal, I would suspect that’s what’s cutting out.

Ain’t it drag when you rebuild an engine, only to find out the ancellary components start to give out?


Right off the bat, I’d assume ECT (engine coolant temp) sensor. It reports the engine temperature to the computer and when the engine is warm enough, the computer comes out of open loop mode and starts taking readings from the O2 sensors.

Secondary to that, it could be an ignition coil or TFI module.

I’ll second Tester on the module since you have one of those TFI-IV vehicles.