high idle

[MNSy2899]

So my truck seems to like to idle high. It has tended to do this for awhile. When it is in drive and I let off the brake, it wants to move on its own. Right away i am thinkin vac. leak. I have a new kit on the way, but is there anything I can check out on Diacom/underhood in the meanwhile that might be the culprit? Sometimes it likes to idle higher than at other times. When I put it in neutral while I am driving it likes to rev up to about 1500 rpms and stay there for awhile. Obviously the tranny also doesn't downshift as smoothly when it does this either. Is this going to kill my tranny if it gets driven like that? Thanks for the help and anyone who could lend their scan tool sxpertise would be greatly appreciated.

Adam
Sy #2899
Eden Prairie, MN

 

[myclone]

How many miles on your truck? If it has higher milage then the IAC could be stuck or have build up/trash in the seat/passage in the throttle body. The IAC itself could be giving up on you also. You can pull it out and clean it and its passage with carb cleaner if you suspect its only gummed up or has debri in there.

Could be a vacuum "leak" too. Not the "controlled vacuum leak" that the IAC is but an actual leak somewhere. You can spray carb cleaner around the intake, TB, vacuum lines, etc and if the eng RPM changes then youve prolly found the source. Do it while the eng is cool as carb cleaner is HIGHLY flamable (trust me on that ).

If you still have the stock rubber vacuum lines on there then they need to go in the nearest trash can. New rubber lines from the local parts store should do until you get the GP silicone stuff on there. The stocker rubber stuff is junk from age/heat by now so they can easily be a source of your idle headaches.

HTH..

(btw.. if you have a "show quality engine comp you can substitute ether {starting fluid} for carb cleaner to check for leaks. Not nearly as messy but WAY more flamable so be MORE CAREFUL with it than carb cleaner)

 

[Mkid]

Had this happen to me just the other day. Found my brake booster hose poped off at 16lbs of boost.

Malik