High Idle 2003 Trailblazer 4.2l 6Cylinder

My Trailblazer idles 3000 rpms too high at all times. I get a code that has been read at autozone with returned results of P0172 B1 too rich. Is there anyone that can tell me where to start with the troubleshooting process?

Good question. Normally I would look for a vacuum leak on the front three cylinders.

Thank you for the start. I am not an expert mechanic so I would need more information in your answer. I understand vacuum leak but where would vacuum leaks form on the front three cylinders? I have verified the tightness of the plugs, but I do see any hoses to check for vacuum leaks. The engine does not miss, but it will stall once every blue moon. The idle remains at 3000 rpms too high. Any new information that may help.

I will send an update on the prognosis in a day or so. I did find an electrode tip missing from the number one spark plug. I replaced the plugs in April 2009 with original equipment. I noticed as I was checking the plug gap that the small fine point tip on the number one cylinder plug was missing. I am hoping this will eliminate the the idle problem and extinquish the service engine soon lamp.

Check that carbon buildup or varnish at the throttle plate in the intake plenum isn’t stopping your throttle plate from closing. If it is get carb cleaner, an old toothbrush and rags to clean it out.

I will do that also. I have a can of throttle body cleaner. I will send you a note tomorrow. As I read throughout the internet it seems thier are many railblazer idle problems with check engine light.

Cleaned the throttle body and replace the plug with the short electrode. Idles/drives normal, service engine light extinguished.