Now that the cold weather arrived my fast idle comes on with a cold start ......but it takes forever to come off I can drive 20 minutes and temp up to 180-190 before it settles back down .............what controls the fast idle "off point" I assumed it was water temp

Thanks

 

Your ECM controls idle rpm. Here's my file from my 2011 5.3.

 

Great info thanks ......so as I thought coolant temp is a parameter that has an impact on idle speed .....I will check to see if it idles down if I turn off the Defrost ( AC) as its is always on these cold days ......maybe thats why idle stays high ?


Regardles I will do a data log and send it off to Justin @BB as he did the tune

 

Idle speed is based entirely on coolant temp, gear and ac clutch