Help from gear heads

[turbomangt]

I just noticed lately that when I'm sitting in idle, my engine/rpms's will increase then drop down on its own. My foot NOT on the gas. any idea why? should I be concerned about it? Thanks

[COP TZER]

i don't think there's anything to be concerned about, i know in the winter this happens to heat up the engine faster. Are you talking about when you come to a stop and the rpm holds just around 2,000 then drops???

[jramosGT]

As long as it's not oscillating up and down, should not be an issue. If it is, likely something in the smog system leaking, like the EGR valve.

[Exhaust Depot]

Engine loads are constently changine. Fans kick on, A/C kicks on etc. Puts a heavier load on the Alternator which inturns puts a load on the engine. A/C as we all knwo puts a load on the engine.

[turbomangt]

its more like when I'm at a light or idle and it doesn't drop, it goes up, or revs higher, just a few seconds , then comes back down. I didn't have air or changed any functions while this occured either. I will watch it closer/ Thanks guys

[kgdptblue]

My 01 did this and my 03 does it also..

[Cal Cruzer]

That is what they call a "hunting idle" in the Mustang community. Usually a bad or dirty sensor somewhere in the fuel injection. Most often a dirty MAF sensor, but we use a Speed Density FI system not a Mass Air system at least on the GT). I would see if you have any codes indicating problems. Could be an O2 sensor.