I have a 2001 Supercrew with the 5.4L motor and about 69,000 miles on the clock.

The truck has never had a mechanical issue until the following: Recently, when I start the truck, it idles up around 1500-1600 RPM for 15-20 seconds, then slowly comes down to 900-1100 where it sits until I put it in gear.

The idle will also surge or fluctuate, like someone's lightly pressing on the gas pedal and then releasing it.

If anyone has any idea what the problem might be, I'd love to hear it.

Thanks.

 

Try cleaning the IAC.

Regards

Jean Marc Chartier

 

I just cleaned my IAC yesterday (I also have a 5.4) and it was a real pain in the a$$.

So my suggestion to you is while the truck is running and idling funny lightly tap on the IAC with a long heavy screw driver. If it fixes your problem then you know what is wrong.

If there is no change I would suspect a coolant temp sensor or cylinder head temp sensor.

 

it could be the idle air controler (iac) or most likely it is the pcv hose leaking vacuum where it hooks up to the intake that hose is bad about leaking

 

How about the throttle position sensor? I've seen that sensor create that same problem and not throw a code. You might want to check that.

Dan B.

 

I have a 2001 supercrew 4.6 mine does the same thing. I cleaned the iac no help. Then replaced it with two different new for iac's does the same thing. Checked codes no codes. Hade the dealer check for bullitans none, Also looking for ideas, hate to change alot of parts with no real differance. my truck only seems to do this after it sets for about one houre in hot weather. starts pefict any other time I have an auto tap and have monitered sensors I dont see anything that seems to be a problem. I wander if it is not a computer program problem????