this is a difficult one to explain.. ok, so my "Service Engine Soon" light has come on and shut off on its own a couple times since i got the Blazer (LS, 4.3L, 4x4). about 4 weeks ago, it came on and hasnt shut off since. the scanner said it was just emissions. it was like PR440 or PO440 or somethin like that..

since it came on, the things been idlin high on the days that it is 30 degrees or lower. could this be a vacuum line that worked its way loose? im a diesel guy, so i dont know much about vacuum stuff.

heres what it does---

when i roll up to a stop sign, i usually shift to neutral and coast to the stop (just somethin i was taught to do to lower rpms and "save gas", not sure if it works). on the cold days, when i do that, it idles up between 1200-1500 rpms. it idles that high even when i stopped in neutral or in Park. when the days are warm, it idles fine. but the light stays on.

any ideas on what i should check? the thing runs great other than that. thanks for any information!

 

Good day! Search this site as the answer is here,but right off it sounds like an IAC or TPS issue, a vacuum issue will give the same symptoms,but all the time,not just on cool days.There are other possibilities as well...

 

could you possibly point me in the direction of what to search for? since theres multiple possibilities, its hard to figure out what to put in the search box.. Thank you!