One of the biggest issues with the 4.2 I6 is the throttle bodies get filthy and it causes all sorts of codes, issues, throttle response slowing, and general just not running right feelings.

It is simple and should be done every 20,000 or so miles.

One of the biggest issues after unhooking or changing the battery is that people say they dont run right and 95% of the time it is the computer not liking the dirty throttle body, where as the computer had learned it before being disconnected.

Take it off spray it down and wide it down carefully and reinstall. I know there are several good write-ups out there. I will do one next time I clean mine, but pm me for a link if you need it.

 

I need to clean mine soon, thanks for the reminder.

 

I recently replaced the battery and altenator because of failure to charge. When I replaced the altenator and started the engine , it flucuated and stopped running at idle. It did this for about three times in the garage. I ran it on the highway for about 10 miles at 55 MPH and it has not come back. Is this normal or should I be concerned. Thanks JHH

 

Computer was prolly relearning the dirty throttle body. I would unhook the battery and clean it up and see if it helps it run smoother and the mpg may be a shade better.

 

this sounds like a issue i noticed today with a '04 trailblazer. blower motor would stay on with engine off, so battery was unhooked to prevent battery from completly going flat. now it barely idles, 500 rpm and will stall when first put into gear. you would think that with a air filter in front of it, the throttle body would stay clean, but ive seen dirty throttle bodies before on other vehicles. never seen one cause poor running after a battery dissconnection.