I have a 2000 Expedition with 4.6L and 52,000 miles. It seems that the idle searches between 700 and 1000 with the a/c on. With the a/c off it idles at 700 with no searching. I am suspecting the IAC valve but I don't want to pay 100 dollars for the dealership evaulation when the part is 125 dollars. The a/c operates normally. This is my first post so any help would be appreciated.

 

Does it do it when the engine is warm? If so, it's prolly not the IAC. Not too sure where to go from there, maybe some sensor. Any more you can say about the symptoms or overall truck condition, any mods?

 

You ever changed the fuel filter? Cleaned injectors? With the way most PCM's keep track of things I would suggest a weak spray pattern from the injectors.


Or maybe the air needs charging. seeking is a result of clutch kicking in and out frequently. Usually means low charge.


Hope this helps

tom

 

I'm not so sure that it may be mechanical. I had the idle surge with my A/C on and off. I had to take my truck in because the CE light came on because of the fuel mixture being rich. They reprogrammed the computer and that corrected the surge . However, if my A/C is on, guess what. . . I bounce between 700 and 1K rpms when I come to a stop.