xkikbxr

4.8L auto 4x4 extended cab. On cold mornings the truck starts right up, revs to about 2300rpm then falls down to 300-400rpm then back up to the 2300rpm. It'll do this for 5 or 10 minutes until warm then it runs fine. It was suggested that it was the IAC. I changed that today and now the truck will barely start without extended cranking. once started it will either jump up to around 2500rpm then die or it will not want to idle more than 300-400rpm until it decides to run right and then the idle is around 500rpm. I can shut the truck off warmed up come back 5 minutes later and it will idle very low and die unless I keep my foot on the gas. Did I get a bad IAC or do I have to manually adjust the idle now. Is the idle even adjustable on this truck? Thanks for any information you can supply.

xkikbxr

I still haven't figured this out. I thought maybe I had an intake gasket leak. I sprayed carb cleaner all around the the base of the manifold when the truck was cold. There was no change in the idle so I don't think I have a bad gasket. I ran all the vacuum lines, none were broken or had a hole that I could see. I sprayed the carb cleaner on all the connections and had no change in idle. I'm wondering if I could have gotten a bad IAC? Any thoughts would be helpful here. I know someone has to have had the same problem with their truck.

xkikbxr

Thanks for the help guys. In case you're interested, it was the intake manifold gaskets. Took about 3 hours to change over. If you need to do it yourself. Make sure you buy the Felpro brand high performance ones they're make with the steel and not all that plastic crap. Make sure when you torque the manifold that you go from left to right front to back. first pas is 44 in pds second pass is 89 in pds. Hope this helps someone.

heathconder

i have the same issue. my question is how cold of a mornings are you talking. how did you know know it was the gasket. thanks ill see if that helps.