I have a 1998 F150 4.6L with 93,000 miles. Within the past 2,000 miles I've been having a strange, what I would call, idle problem. When the truck has been running for about ten minutes or so the RPM's will jump up to about 1500 or alittle higher. The strange part is, is that it dosen't sound right. Its more like a humming noise than a reving noise. I have a intake kit on it and it sounds like its coming right out of the air filter. It does this while it is Idling and if I'm going down the road and just let off the gas. If I tap the throttle the sound will go away but come back the next time I get off the throttle. It also will do it just by shifting it from drive to reverse. I'm alittle perplexed, maybe a sensor? If any of you have any ideas your help would be greatly appreciated. Thanks.

 

Welcome to the Boards!

That is a strange problem, try checking all your connecions, hoses, wires, etc... for the intake kit. I don't own a newer F150 but i have heard that sometimes the IAC (Idle Air Control Valve) can get stuck on these trucks sometimes. I don't know for sure if this is contributing to the problem but it couldn't hurt to check it out. If all else fails, take it to the dealer or take it to a Auto Care shop you trust and know. This is just my $.02. Good Luck!

91

 

I've got an 02 with only 21k on it and I had to have the IAC changed out about 2 weeks ago. Mine would idle up and down and up and down while in park, but when in gear would do OK.

When I would let off the gas while at cruising speeds, it would seem to hang on for a little while.

The IAC is right behind all the crap on top of the intake manifold and doesn't seem to easy to get to.

That's the first place I would look at.

Creole