2005 4.3 Silverado Intermittent cold start idle Revving up and down 900-1500 when cold. No DTCS. Fuel trims good.

[colin7761]

hello, thanks for your time. i'm trying to figure out an issue that happens sometimes with my bros truck. It has a cable throttle. often, on a cold start the truck will start up fine, then rev up to 1500ish  then down to normal rev range, then back up to 1500. It will do that over and over again and as it warms up the rev up starts to get lower. So as it gets warmer, the engine will rev up lesser and less, until it settles down at normal rev rpm within a minute or two. I've checked all the wires and connections to the TPS and the IAC and they are all good. Some of the wires have been replaced due to damage, i checked the connections and they all check out. The operation of the TPS seems to be good too. No DTCs set. I believe the revving up and down is the iac opening and closing repeatedly, I'm just not sure why it would do that. When warm, the truck starts up and immediately idles perfectly. Just hoping someone has come across a similar issue in the past. Thanks again!

[richard wysong]

Dirty throttle plate, clean that and the IAC and do the idle relearn

[colin7761]

would a dirty throttle plate really cause those specific symptoms? the throttle plate has been cleaned fairly recently.