Stalls after warm-up

89 4L auto runs fine until throughly warmed up and then will die and not fire up again until 5 minutes or so of cool down. Its in the 20's F here in Anchorage and this has been a problem after about 6-8 miles of driving. Will not start again with out WOT and even then it seems to have to cool down before it wants to behave. Lots of bucking and stumbling and having to feather the throttle to get home what an adventure that is in a snow storm and holiday shoppers. Any ideas here? All are greatly appreciated, and a Merry Christmas too all.

Hallo. I only know, that there are 2 parts, that can give problems when hot: The Crank Position Sensor and the Ignition Coil. Maybe to search in that direction. :eyes:

Merry Christmas from Holland.

Could be a faulty EGR valve...

Hi,
I would put serious money that it is your CPS that is the problem, I had exactly the same symptoms, I had a new CPS fitted and it has been running perfect the last couple of years.

I eventually figured out what causes the problem, the CPS is fitted to the bell housing, which expands as the engine warms up, this moves the CPS further away from the fly wheel which is what generates the magnetic pulse that is fed to the computer. A new CPS can handle the expansion but an old one cannot. Hope this helps, and a Merry Xmas.

Info on the CPS
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Crankshaft Position Sensor: Common Symptoms if bad:

*Both the fuel gauge and or voltage gauge may not work/display

*It is possible that you may see a No Bus on the odometer

*You will have no spark. Fuel pressure may check okay but fuel won’t get to injectors

*Sometimes the OBDII code reader has trouble connecting to /reading codes

*Crank sensors can be intermittent; "thermal failure" is pretty common. Means that the sensor fails when engine gets hot, but works again when cooled back down. Be aware of this when testing as if you have a sensor that suffers from thermal failure, it will probably test GOOD as soon as it cools down.
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CPS TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (A-B-C) looking into connector left to right with the part with the notch in the middle on the right) Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

CPS TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1

Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.


Test # 2

You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

Thanks for the help on this. I got to thinking about what Jeepcreep posted so took my long prybar and 20 ounce ball peen located the sensor from the engine side and placed one very smart hit to the sensor plate. Drove around for at least an hour today in single digit temps without any symptoms as before. Tomorrow at daylight I will confirm that the 2 mouting bolts on the CPS are tight and might even change out the CPS if I feel real tough. Will post again if this tweek does not last long. Keeping fingers crossed.

Tweak did not last long! Installed a new CPS tonight in a warm garage and have a few tips. First of all if you have a buddy to help all the better here goes: one 11mm flex socket with a magnetic insert one 12" extention connected to that then a universal swivel adapter then another 12" extention connected to a ratchet all 3/8" drive. The buddy can confirm that you are square on the bolt from above and the magnetic insert will not let anything fall away. The reverse is so simple that this process with these tools took about 20 minutes start to finish. I hope this helps someone here in the future.
Thanks everyone and a Happy New Year.

I used 3 12" extensions and a universal at the 11mm socket...

neonrog yes this will work but having done this more than once I was looking for an easier method and what I described above is the cats pajamas.