2002 GMC Yukon idle surge issue

[JAC43]

My 2002 Yukon 6.0 w/ 80k miles will fluctuate idle up and down quickly between 500-1000 RPM at times, and at other times it idles smoothly. It is not throwing any codes. No issues with lack of power or unusually bad mileage.

A vacuum leak maybe? Bad TPS? Anyone else experience a similar problem?

Thanks

 

[cchase]

Bad TPS will likely throw a code and cause drivability issues.

Vaccuum would be an easy first thing to check although the fact that the problem is intermittent is interesting.

IAC possibly?

 

[mechanicx]

Cleaning the throttle body might help.

 

[demarpaint]

IAC, and a possible vacuum leak is where I'd start looking. Cleaning the throttle body won't hurt either.

 

[NEOhio_Bob]

Originally Posted By: demarpaint
IAC, and a possible vacuum leak is where I'd start looking. Cleaning the throttle body won't hurt either.


What he said...GM V8s of that vintage had plastic intake manifolds that cracked and intake manifold gaskets that failed, so vacuum leaks are common when they get some age on them.

 

[George7941]

A scan tool would help a lot for checking manifold leaks since intake leaks will show up as positive fuel trim values.

Disconnect the MAF and see if it makes a difference.

 

[mechtech2]

Vacuum leak is high on the list!
So is a dirty/sticky idle air controller motor and valve.
TPS is possible - easy to check or change.

 

[stroked93]

clean the throttle body its a known issue among the LS engine forums.

 

[MrCritical]

And a clean fuel filter doesn't hurt either.

 

[Jim Spahr]

I concurr with demarpaint. Sounds like a classic IAC problem. Try cleaning it and if that doesn't work a new IAC. Clean the throttle body where the plate touches and always check for vacuum leaks. PCV cleaned and dried and checked would be great.