Suddenly Developed High Idle

[1999Yuk]

Hey Everyone, new to the site.
99 Yukon Bone Stock 5.7 litre. Intake coolant leak repaired several months ago.
About 3 weeks ago engine rpms would hang around twelve under normal acceleration and vehicle acted like cruise was enagaed. Idle would not return to normal till after a 10 - 15 seconds after a full stop at a light or intersection. Seems to be getting worse about returning to normal when stopped and maybe even higher than 12000 rpms.
A friend suggested maybe a vacumn line leak or TB is sticking.
Anyone dealt with this issue recently? Send me some feedbback.
Thanks

 

[blueflamed03]

vacuum leak?

 

[crmzendrgone]

Vacuum leak or IAC motor is failing.

 

[drowndindreams]

Definitely sounds like a vacuum leak to me, check your hoses first.

 

[1999Yuk]

Ok.Thanks for the input, I'll start there. Another tech also suggested the TPS but will start with the easiest first and checking vacuum lines and intake..

 

[black95]

+1 vacuum leak

 

[ravingmadman]

Vacuum is probably your issue. Your engine will also do the exact same thing if your alternator is starting to die. If the system reads low voltage, it revs the engine up for a little while. Check your vacuum lines, and have your local parts house do a free electrical system check. My money's on your vacuum system though.

 

[TahoeJim]

Mine was doing the exact same thing and it started out of the blue 3 weeks ago. And just like it started, it suddenly stopped for no apparent reason 2 days ago. No one's been under the hood, nothing touched. No clue.