Ford F150 - Blinks 4 times and revs up

I thought for sure after someone told me it happened to them and it was fixed by changing the IAC (Idle Air Control). Well, I changed it tonight and it's still doing it..

It starts up OK, check engine light flashes 4 times revs to 2,000 rpm, slows down eventually or sometimes rev's back up then eventually goes back to a normal idle. Does ANYONE know what to check next? The only code I get when I test it is 172 in both KOEO and KOER.

thank you in advance for the help.

give the throttle position sensor a try

http://www.fordf150.net/forums/viewtopi ... hlight=tps

Always pull the codes & do some diagnosis before buying any parts. It's cheaper, faster, & more effective. That link has most of the code definitions, and a link to the full list.

172 R,C Right HEGO indicates lean

Sounds like an exhaust leak, or low fuel pressure, or a vacuum leak, or damaged wiring, or MAYBE a worn-out HEGO (but don't buy a new one without testing the old one first), or something else. But I doubt it's the TPS or IAC.

I tested the IAC with the Haynes manual and it tested out bad, not every time buy it did a couple of times so I changed it just in case. (and of course figured that would be the fix)

I also tested for a vacuum leak with my propane torch and nothing showed up for that.

Next will be a fuel pressure test, just need to go out and buy a tester.

As for wiring, I'll start on that this weekend.

Thanx for the ideals it's very much appreciated.

something i forgot to mention and it's probably very important for diagnostics,

Until the engine is at optimal temp. I have a lack of throttle response. (it bogs out at lower RPM) At more than half throttle it has all the power neccessary to "high ball".

Use a mechanic's stethoscope or even a short section of garden hose to find vacuum leaks - it's MUCH more effective & safer than spraying flammables all over the engine.