200 Suburban idle problem

My wife's 2000 K1500 Suburban recently developed a problem with idle speed. OK on startup, idle increases to between 1000 rpm and 1500 rpm when warm. Not good for brakes and transmission. Engine is 5.3 liter with 60k and runs well otherwise. No check engine light or other symptoms. Any ideas?

I would look for the possibility of a vacum leak.

I would look for the possibility of a vacum leak.
GMMerlin I need your help on a 1989 k1500 5.0 tbi stalling at idle. Can you help??
Tom

I have a 2003 and had a similar problem. The intake manifold gasket was leaking. I changed it and the idle problem went away.

I have a 2003 and had a similar problem. The intake manifold gasket was leaking. I changed it and the idle problem went away.
Thanks !! It's fixed!
The problem was weak magnets in the Dist. this a problem that is just now showing up in 1989 C/K trucks and some V8 GM cars! GM knew about this problem and knew that it would take years(10+) for the weak magnets to degrade to where it would start causing a problem with weak output from the pickup coil. If the Ohms on the pickup is 500-1500 its ok. but the real test is output! test at the pickup plug(unpluged) set your meter to AC and 2 volts or so...at cranking(won't run) 550-1000mv should show on the meter.I had 250mv and that was NOT enough to drive the module at idle! Rust,oil,age kills magnets! Weak from NEW is no help! thanks GM! so beware of a used one!! only replace with a rebuilt one the replaces the stator (magnets)...my rebuilt one tested by hand over 1000mv ac!! the old one maybe 450-580.. remember that other years and makes can have this problem! Oil comming up the shaft(TSB's on that for years!) gets into the magnets and kills them. rust can kill them too! One more thing. If you have no idle or bad idle on a TBI system have the module tested. the module has a LOW RPM part inside that can fail! Auto zone can test it! my module was bad on that Low RPM.I replaced it thinking that OK here is the whole problem. No!! same thing! then i found out about the magnet problem GM had! the rebuilt Dist comes complete(new module) so i have a $45+ module as a spare now. Testing for Output from the pickup and not just OHM's(tested good 850) would have save me $45+ and time testing other things because the pickup showed good and a new module to replace the bad one(low rpm side)at the time looked like the fix.. If i had only tested Output first and seen that 245mv i would have just got a rebuilt Dist for $123 and be done!
If you need any help on the best order to start you testing of parts please E-mail me!! [email protected]