1991 Ford Explorer warm startup problems

Did you do a diagnostic test on it that said you needed the O2 sensor? If so, you may have more than one.....in mine, the check engine light came on.... and brought it to a repair man who told me he needed to replace the sensor.... it lasted about 2 weeks when the light came on again... brought it back and he replaced the second one and that fixed the problem.... nothing since..

Fwed

I didn't check engine codes, I just thought it was a fuel mixture problem or something, and started replacing stuff from the cheapest up, and it needs a new O2 sensor about every 80k miles or so anyway. I was only aware of one O2 sensor in the 1991 explorer, I could be wrong though.

Typically when you have trouble starting up after a vehicle is warm it is a good indication your starter is going bad.

But if it were your starter it wouldn't be shutting off after its running.

How many miles do you have on the vehicle?

Its not your starter. Try the Engine Coolant Temperature sensor. The voltage drop across this sensor corresponds to the temp of the engine coolant. Take a voltage reading of this sensor with key-on-engine-off (engine cold). Start the vehicle, then monitor this same voltage as the car warms up. It should change, as the temp changes...Jim

I don't have a voltage meter, so I just replaced the sensor. It didn't fix the problem, but the old sensor needed to be replaced anyway. After I re-started the car when it was warm after replacing the sensor, it wanted to die and acted like it normally would while dying but barely hung on, so it got a little better. When I pressed on the gas, it didn't go, and kicked a little, then went and kept kicking, like it is starving for fuel still. Any other ideas?

This is a tough one! I'm assuming that there are no problems when it is started when completely cold. 2. That it runs fine after its first start in the morning? 3. That the probelm only presents itself once it is shut off, and a restart is attempted prior to it cooling completely?

Yes. It starts just fine when it is cold. Immedietely after I restart the car when it is shut off, it goes fine; it is just after 15 or more minutes, until it is very near cool, that it won't start right.

I bought a code reader for my car for $40, it was cheaper than having the codes read in a shop. the KOEO and KOER tests turned out just fine, said there was nothing wrong. I am stumped.

I bought an engine code reader for $40. It was cheaper than taking it to a shop to have the codes read. It read good for the KOEO and KOER tests. I guess I will have to wait until it breaks, because I'm out of ideas.