cj8scrambld
06-02-2002, 05:33 PM
Can anyone shed some light on this problem? My 1994 KBlazer 5.7 TBI has an occasional high idle speed and occasionally runs with an irradic idle speed..like 500 rpm to 800/1000 rpm up and down going by the OEM tach. I have changed the IAC and the engine coolant temp sensor. Should I look at the EGR valve as a source? Or, can it be a TPS? It has 72,000mi on the clock. I do not get any codes or "check/service engine soon" lights. Any ideas or tips would be appreciated, thanks. John
Twiztid
06-02-2002, 08:27 PM
Sounds like your TBI casting is worn.
Grab hold of the throttle shaft and wiggle it.
It should rotate freely, but have no movement other than rotationaly.
If the casting is worn, the throttle shaft can get out of line and intemitantly wedge the thottle blades slighly open (slightly off idle) and cause your irratic idle concern.
Have the throttle body re-bushed at a local repair shop (G.M. dealers can/should be able to do this repair)
It could have sucked the TBI to manifold gasket, also causeing a high idle, possibly irradic idle too. But usualy when the TBI gasket is shot, it will have a high steedy idle speed. (thats why I'm thinkin' it's the throttle body casting)
-K-?
BlazzinOR
06-02-2002, 09:05 PM
Twiztid has a good idea............for sure. Regardless of if that is the problem, get yourself either a scanner (like one from www.autoxray.com ) or some software/cable/laptop hookup to watch what is going on with your motor/ECM. Gotta have one of those to 'see' what is up............like if your IAC motor is in need of re-setting. Also go to www.thirdgen.org for info and tips on what is up and how to fix it..........like resetting the IAC and TPS..........articles on how to do those things there.