I have a 2005 Chevy Silverado 1500 with the 4.8L V8 in it. it is a great truck and runs great, but it has a slight problem. for whatever reason, when the truck is warm, and i shut it off, then go in the store or whatever for a couple minutes, then come back out and start it up, the RPMs skyrocket to around 1800-1900. they go back down again in a matter of 3-4 seconds, but that cant be normal. it does have an exhaust leak at the manifold, it needs a new gasket. other than that the things i have tried are, clean out throttle body, clean throttle plate, clean idle air control (port?). and it still does the saaaame thing. anyone have any ideas? any help with this would be much appreciated. thanks!
ddog96mn
I know this is a super old thread but did you ever solve the problem? I have the exact same issue, same engine, only mod is volant CAI. :?
The CAI might have something to do with it. But unless the high idle problem started at the same time or soon after installing it, I wouldn't look there. Just throwing this out there, but the throttle body can cause erratic idling and it may just need a simple cleaning.
The problem actually began to occur immediately after I cleaned the throttle body. The CAI had been on the truck for about a year before the TB cleaning. HOWEVER, I seem to recall my mechanic raising the idle rpm before I installed the CAI most likely to compensate for gunk and buildup on the TB and IAC valve. Now that I have cleaned both, could the computer be overcompensating for these changes. I pulled the ECMB and ECM1 fuses to reset the computer, but it seems the computer just relearns back to the problem the OP stated. Idk if my mechanic used a scanner tool or the TB adjusting screw to change the idle RPM
OK. I think I know what caused the problem and possibly the fix. The problem was caused by how you cleaned the TB. When you cleaned it, you should not have moved the butterfly valve which in your case, I am guessing that you did. When you did that, the truck became confused as to the position of the valve and so now it is having problems controlling it. That being said, the truck in theory, should eventually relearn the positioning and it will all smooth out. Or you can take it to the dealer and they can recalibrate it.
Yeah I moved the butterfly valve quite a bit when I was cleaning the TB, I will take it to my mechanic and ask him to recalibrate the position. Thanks esox07
He will need a special tool I believe. The average garage type mechanic might not have it but a dealer or big service shop will. Good luck and report back when you get it reset.
This is super old but for anyone who searches this thread and wants closure here was the fix:
Mechanic found the issue. Trans kickdown cable had too much tension in it and the metal tab that acts as a stopper for the mechanism the accelerator cable pulls was bent downward. Relieving some of the tension and bending the tab so it rests flat on the housing fixed the revving at idle.
Mechanic found the issue. Trans kickdown cable had too much tension in it and the metal tab that acts as a stopper for the mechanism the accelerator cable pulls was bent downward. Relieving some of the tension and bending the tab so it rests flat on the housing fixed the revving at idle.
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