lacroluk

Alright guys having some trouble with my baby. I have a 2003 F150 5.4L with mainly a idling problem. When I first start it up after it is cold it runs just fine. After I'm driving and it warms up, when I put it into park it will start revving. RPM's goin up and down from like 1200 down to like 300. Does it to a lesser extent intermittently when I'm driving it too. Thought it was the IAC acting up but I dropped a new iac in yesterday. Please help.

101stmp

Try cleaning the mass air sensor and check the emission hoses for cracks and such.

Blrea86

Or the iac valve

Red-Ford

My brothers truck did that while driving, it was a vacuum line with a split in it. couple dollar fix. He has a Dodge, but none the less that is where I would start.

Blrea86

Yes vacuum lines !

A7X

I think you may have gotten lost

https://www.f150forum.com/f6/2003-f1...d-help-282807/

Jbrew

Taught that looked framiliared...The stench gave it away..brain fart for sure.

OP, just search..bet you run into yourself...like daja vu. Or in this case,- daja dui...