Jim Grant's Tech Tips

99 Ford Expedition, High Idle, Then No Idle

Q: What would cause a ‘99 Ford Expedition when starting to go up to 1500 RPM and then drop down and stall? The idle should come back down to about 850 RPM or so but instead it will die unless I keep my foot on the gas. But, when it warms up you will hear the idle go up a little and you can slowly let off and the idle is fine. The problem does not occur when the temperature is warm outside.

Eric

A: First off, I would suggest checking the minimum idle speed. It will likely be low due to a build-up of carbon deposits in the bore of the throttle body and on the throttle plates. Ford claims to put some sort of magic coating to prevent this condition. But, that magic seems to wear off fairly early. With clean throttle plates and bore, the minimum idle speed needs to be checked and adjusted if needed. Minimum idle speed is where the engine will idle without the computer’s involvement. This check and adjustment is performed with the idle air control motor (which is the thing the computer uses to control idle speed) disabled. If these base settings are okay then the idle air control motor itself is a possibility. These units, when failing can be as erratic as the weather. With your vehicle the basics must be clean and correctly set. After that the part that the computer controls is suspect.