2000 Expedition 5.4L - This does not happen everytime...

When the vehicle sets overnight in either either warm or cool weather and is started for the first time it seems to stumble, not come up to full idle for a few seconds. If this were a carburate engine I would think there is a choking problem. After a few seconds with the engine running under low power it idles up to full idle normally for a cold engine. There are no codes in the OBD. Plugs and coil packs where replaced about a month ago. My thoughts are that it may be one of the following:

idle sensor?
fuel pump pressure?
fuel filter?

Anyone seen this or have any thoughts on what it could be, again it does not do it everytime?

Thanks,
Jeff

 

You're on the right track. Most likely the IAC valve, but a new fuel filter is cheap, easily replaced and very worthwhile.

 

jtarkington, Sorry for the late reply, but I just had something similar fixed on my 99 Expedition. It seemed any time the RPMs dropped below 1000, the engine would stall. I like to work on my truck myself, but I was having my mech look at my transmission, and he looked at this problem at the same time. He just cleaned the idle sensor, and it is fine now. Hopefully, you can try that before trying too many more expensive things, but I'd imagine you've already tried several things.
~Jason