Truck is 09 F250 CrewCab 4.4 5.4L. I noticed the other day when shifted into parking gear, the idle starts at approx 600 for about 10 seconds, then surges to approx 750 for 5 seconds then it goes back to 600, then back up to 750 etc... (this cycle repeats indefinitely). The idle is fine if I'm in gear and have the brakes on, it's only when its sitting shifted into Park that the idle surges like that.

I'm not sure if those are the exact RPM numbers it was surging at but it is close, noticed it the other day. Took it to Ford last week when I got an oil change and mentioned it, they said there was a TSB and reflashed my factory PCM but it didn't seem to do a damn thing as the surging idle is still there.

The TSB was 09-7-12 and says:

"Some 2008-2009 F-Super Duty 250-550 vehicles equipped with a 5.4L or 6.8L engine and built on or before 3/12/2009, 2008 F53 Motorhome chassis equipped with 6.8L engine and either a 5R110W or M6HD transmission may experience a rolling idle or idle speed dropping below specification, malfunction indicator lamp (MIL) along with diagnostic trouble codes (DTCs). The DTCs include the following: P0111 (Intake Air Temperature Sensor 1 Circuit Range/Performance), P1635 (Tire/Axle Out of Acceptable Range), P0054 (Exhaust Gas Temperature Sensor Circuit - Bank 1 Sensor 1) or P0456 (Evaporative Emission System Leak Detected - Very Small Leak)."

Truck seems to drive fine and is not throwing any error codes but the surging idle has me concerned. Anyone got any ideas as to what this might be? Only got about 6 months left of the factory warranty, need to get anything thats wrong fixed before then!

 

How many miles do you have on her?

 

Approximately 25,000, and roughly 2/3 of that is freeway miles.

The only other engine related problem I can recall was an exhaust manifold leak but that was replaced about a year ago and has not been an issue since then.

 

replace the idle air control valve (IAC) they get clogged with carbon buildup

 

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An '09 5,4L doesn't have an IAC. Those were on the 2V gas engines.

Possible causes are the Throttle Position Sensor, Mass Airflow Sensor or an O2 sensor. But, since you're still under warranty do not mess with it. Let the dealer sort it out.

 

That's what I'd hope they would do when I took it in the other day. I think they just searched for TSB's with 'idle' for my vehicle and assumed that was the problem. I'll probably bring it in at the end of the month and see if they can actually fix it for good this time.