95 Explorer very rough when started warm

[hymes]

Hello, when the car is started COLD there is no problem. When the car is HOT there is no problem. But when the car is WARM or Sits for a little while (30 min) after it has been running, it starts but very rough.

So for example, you start it in the morning and all is fine. You drive to a store to do an errand and park it for say 20 mins. When you try and start it again it is (not always) very rough. You give it gas and it very shortly clears up and runs just fine again.

Any ideas?

Thanks
Alan

 

[my98nnj]

Make sure the engine coolant temp sensor is within spec.

 

[Opera House]

This is usually associated with a fuel pressure leakdown. When pressure drops below 20# agas bubbles form in fuel line. An easy test to try is the following. Turn the key to just ON for 5 seconds and then off a couple of times will likely flush any bubbles out. If this works, a likely candidate is the fuel pressure regulator. Some of these had the spring off center and the seat wears to one side and leaks. In normal operation this isn't a problem because 80% of the fuel goes back to the tank anyway. I have hears some people install a push button to operate the pump manually before starting instead of actually fixing the problem. The computer only runs the pump for 5 seconds and shuts off till the engine starts. That doesn't do a lot of flushing or cool down the fuel rail.

 

[hymes]

Make sure the engine coolant temp sensor is within spec.

Hello, you are the second person to indicate that. But there are two temperature sending units listed for the ford. There is one called the "Coolant Temperature Sending Unit" which is on the passenger side and there is the "EEC-IV Coolant Temperature Sending Unit" which is on the driver side.

Which one is the most likely one to replace? and the book talks about removing the "upper intake manifold" to do this. Do you really have to or can you squeeze in and remove and replace?

thanks so much,
Alan

 

[2000StreetRod]

Which engine?

From your description I suspect that you have the SOHC. If so, the sensor nearest the driver side is the one the PCM monitors, hence OBD in the name. The output of the other sensor goes to the instrument panel to display engine temperature. My Haynes' manual states that it is necessary to remove the upper intake manifold to replace either sensor. After replacing the gaskets on my lower intake manifold I agree. I would not undertake the exercise without confirming the sensor was bad unless you also need to replace intake manifold gaskets. You can easily monitor the sensor output via a scanner.

Another possible source of your problem is an injector susceptible to heat. I suggest replacing the fuel filter if it hasn't been replaced in the last 30,000 miles, add a bottle of fuel injector cleaner to the fuel tank and wait 100 to 200 miles to see if the problem goes away.