2000 GMC High Idle and shutoff problem

[fogdog101]

I have a 4.3 with new plugs, wires, cap, pcv, cats, egr, fuel filter, and mass airflow. When I start it in the morning it idles great. I will drive it 1-5 miles down the road and it will cut off one time for the whole day. I start it back up and it never shuts off the rest of the day. Also when I push the clutch, it will idle high until i come to a complete stop at the stop sign and then go to idle. Please help. I have spent a lot of money so far. There is no check engine light.

[maxwedge]

We;lcome to AF. Clean the throttle body and iac for starters. Why were all these parts replaced, to to fix this issue?

[fogdog101]

Most of the parts were replaced by the prior owner. I replaced the cats b/c there were none(which i found out after i bought it) I replaced the cap. What is the IAC and where is it located.Thanks for your help.

[j cAT]

Originally Posted by fogdog101

Most of the parts were replaced by the prior owner. I replaced the cats b/c there were none(which i found out after i bought it) I replaced the cap. What is the IAC and where is it located.Thanks for your help.

the IAC is a motor/valve that regulates the air flow so as to maintain the correct idle rpm....normally every 30-50,ooomi this componet as well as the throttle body are in need of cleaning...use throttle body cleaner NO carb cleaner as rubber will over time breakdown...

IAC idle air bypass...this is at the point where air enters the intake mounted in the throttle body with screws and has a electrical connector...when removed do not try to move valve [pintle]I use a tooth brush...no abrasives here...gentle easy does it cleaning also with the air pleum/rubber removed clean the throttle body and wipe out excess throttle body cleaner and give time for cleaner to vent off before starting hold throttle plate open and you may need a hair dryer to speed this up if cold out..

PCV this neglected componet needs replacing and the hoses are common failure items that cause idle to be wrong...also any air leaks in the air ducting after the MAF will cause many problems with the engine performance.