Surging idle

[mjfoster49]

When my truck is idling, it surges between 670 and 700 rpm. It only does it after it warms up good. It just started doing this the past couple of months.

[Fordoor444]

My truck did the same thing, this sounds kind of crazy but it turned out to be the serpentine belt. I was sceptical, but a new belt solved the problem. This is a cheap fix anyway if that's it! Good luck!

[SCUFFY828]

is maintenance up, is there any codes in system, ipr orings maybe, fuel pressure , need to do some diag

[mjfoster49]

I changed the oil and fuel filter a couple weeks ago. I scanned for codes, and there werent any. It didnt do it with the edge evolution, but when I switched to a DP tuner that is when I started noticing it.

[SCUFFY828]

ive seen tunes cause problems before also, may not be anything to be concerned with

[ns954]

Mine does the exact same thing.No tuner or chip.Does it when it warms up.Not all the time,just every now and then.No codes.CPS has been replaced.

[Sinac]

Call me crazy, but I deal with CAT C9s and C-9s quite often and they have a very similiar fuel system. And 9 times out of 10 when they surge its because they are lacking fuel pressure... They still run fine, just under a load or sometimes idling they will surge between 650 and 750 rpm.