Truck has high idle and gets higher when it warms up? Gets up to about 1600rpm
Dirty or faulty idle air control valve can cause this issue.
A vacuum leak can also cause it. I would check that first.
Thanks it's my buddy's truck! Yah we used carb cleaner and sprayed around to check for vaccume leaks got nothing.
Is that valve in the TB?
Yes. Can't seem to get a picture to down load. Sorry. Google this :: 1999 sierra 1500 idle air control valve --- it will give you a picture of one.
Looking for a Used Sierra 1500 in your area?
CarGurus has 64,792 nationwide Sierra 1500 listings starting at $1,500.
Search GMC Sierra 1500 Questions
GMC Sierra 1500 Experts