2006 sierra 4.8l tb clean idle wont learn

[rob0126]

Hey folks. I cleaned my throttlebody today. now when i crank the engine, the idle goes to 2k for about 2 sec, then idles down.

i tried many idle relearn technics to no avail.

drove the truck, thought it finally learned but when i turned truck off, recranked, back to the same thing as if it didnt learn a bit.

ran fine before the clean using tb cleaner. i didnt get the elect wet either.

i even replaced the gasket with a gm one and torqued to about 7 ft/lbs(book says 89 in/lbs=7.4 ft/lbs).

 

anyone got a clue?

thanks

 

Robert

[rob0126]

btw drove for 10 min 2x. it seems to have almost completely learned, But, when i turn it off, then recrank, it idles up to 2k for 2 sec, then idles down.

 

this is frustrating. i just bought this truck a few weeks ago.

 

it has 143k miles.

[amc31b]

Ugh, please tell me you did not just open the butterfly valve (throttle plate) by hand. The plate is probably controlled by an electric motor, not a regular cable like the old days. If you opened the plate and held it there by hand, you may have made the throttle controller (basically a servo type motor) and throttle position sensor get out of sync and go haywire.

 

If this is what you did, you can try disconnecting the battery for 10 minutes and hope that re-sets the Throttle position sensor. If this doesn't work, someone else here with more experience will have to help you out. The only other thing I could say would be to take it back to the place you bought it and pretend you don't know what happened. That is not the most honest thing in the world to do but if you bought it from a Stealership, it might be worth a try.

 

The proper method for cleaning most modern throttle bodies today is to turn the key to the ON position and have an assistant step on the gas so you can get inside the TB and butterfly valve/plate (whatever you want to call it) and clean it. When you are done cleaning, have the assistant let off the gas pedal and turn the key to off and remove it. Then you can re-start the engine and drive some to let the rest of the cleaner burn off.

 

Let the rest of us here know how you make out so we can avoid this problem in the future.

[rob0126]

I removed it from the engine and cleaned it.

[Silverado4x4]

Sounds like your new gasket is leaking. Also try unhooking the battery for about 30 minutes then hook it back and go from there.

[amc31b]

I removed it from the engine and cleaned it.

 

Good man! Try disconnecting the battery and see what that does.

[rob0126]

disconned the battery. reconnd. same thing.

its like it learns but looses it when engine is shut off. maybe the new gasket is leaking. i tightened to specs and used a gm gasket.

[rob0126]

will update once i figure this out. might try a different gasket.

[rob0126]

Fixed. Found the problem.

 

When I put the Airbox back together, the screw nearest to the radiator pushed the top part of the airbox up, because the bushing inside that stops the screw was messed up.

 

So, the airbox lip was exposed to straight air, hence throwing off the computer everytime it wanted to hold it's learned idle.

 

Solution: put a washer under that screw so it will compress the top part of the airbox with the bottom and sealing it to the bottom part, sealing the system to the air cleaner.

 

I knew it had to be a changing variable for the computer to learn the idle, then loose it at random.

 

Hope this helps!

 

(EDIT: I did change out the gm gasket for a felpro gasket, but I dont think this was the problem.)

[amc31b]

Thanks for the follow up. Glad you got it fixed!