Throttle body and high idle that takes time to get normal

[dla442]

A throttle body question. I cleaned the TB the other day. Disconnected the battery first! Removed and cleaned it. Reinstalled and torqued it down. Plugged in and connected battery. All was well for the first few minutes. Now I noticed idle is higher and won't come down like it should. While driving and foot off gas it is high about 1200rpm. When slowing down, the idle remains high and will calm to 650 rpm after 5-8 seconds at a complete stop while in drive. When driving down road and put in neutral, the rpm is 1300 and does not go down. When in neutral and slowing to a traffic light the rpm's stay high until the 5-8 seconds of it gradually dropping. I disconnected all battery terminals again and let it sit for hours. All was good for about a day, now the high rpm idle is back. No vacuum leaks, no cel light. Runs fine just idles high when slowing down and makes trans downshift a bit jerky. Coincidence on the TB maybe going bad, a relearn on PCM. All was fine before the cleaning. Any ideas?

 

[Robbabob]

When the battery is disconnected, the system must re-learn how to function. I have seen the default be a high RPM, rather than stalling low.

Do a lot of neighborhood driving where you have a lot of stop signs, and get to complete stops each time. Get up to 45 between neighborhoods and do it again. It may take a few days at a neighborhood per day, but it should get back to normal. If not, come on back and give us details on your driving cycles and what the rpms are doing then...

Good luck!!

 

[{tpc}]

This situation occurred to me after a TB cleaning just the other day (you can find my thread about it in the vortec 4.2 subforum). Anyways, I didn't do anything to it other than a pcm fuse pull followed by more stop and go driving. It took a couple days, but eventually returned to normal operation.

See this thread for more on it:

http://gmtnation.com/f25/clean-throttle-body-now-high-fluctuating-idle-10306/

 

[gmcman]

To highlight the relearn.....follow this step by step, don't touch the gas until it's time.



Pull fuses 10&28 for about 15 minutes then re-insert the fuses. Turn the key to ON and let it sit there for about 5 min. During this time do not start the vehicle or touch the gas pedal, just turn the key on, you will hear the TB make a series of noises during this time. After about 5 min, start the engine and don't touch the gas pedal, let the engine idle for about 10 min. Then go drive it.

At no time touch the gas pedal until you are ready to drive it.

Edit: Make sure the A/C compressor is off, no front defrost or foot/defrost symbol. best to keep HVAC off.

 

[dla442]

Cheers..will try these steps and advise.