Hey all,I have an 04' f-150 4.6,lately it has started to have idle probs.I'll be at a light and it will drop to around mid 400's then shoot up to around 850. then it runs normal for a couple mins until it does it again.I was told it was the up idle control sensor.Is it? and has anyone had to replace one before.Just wondering what I'm up against.Any info will be greatly appriciated.

 

Hot? Cold? Long lights? Morning? Night? On the brakes?
Throttle positon sensor, Coolant temperature, Idle Air Control motor
Possibly packed fuel filter
MIL light on?

 

TPS or IAC. Have it checked for codes. You have a K&N, or other "oiled" air filter? This can make the MAF sensor dirty and cause problems.

 

Hey guy's,thanks for taking a min to respond to my issue.It happens right at start up,after its been running etc...there is no particular time.I do have a k&n cold air kit on the truck and know about the oil and sensor,but I have not treated it since I have put it on.Anything else it could be? thanks

 

almost the same thing happend to me this morning. i am drifting towards a red light with my rpms around 600 and decreasing and i am braking slightly. all of a sudden i realize that i am not slowing down fast enough. i thought my brakes where fading until i looked at my tach and saw my rpms at 1300! WTF? the truck has 1200 miles on it and the engine is stock. i know people have had problems with dirty IAC valves. but at 1200 miles ?????????

 

This is likely your problem. Start here.

You have the easiest solution. Take it back. It's under warranty. Screw working on it yourself!