1995 GMC Truck low idle

1995 GMC TRUCK
211,000 MILES • V8 • 4WD • AUTOMATIC
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DRACOTATS
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  • 1 POST
While driving in overdrive and on cruise, I do notice a slight miss. When I start to slow down to a stop, the idle slows to about 300 - 400 rpm as to stall, but goes back to 1000 - 1100 rpm when I stop. I have replaced the PCV, IAC and TSC and am using an additive for the injectors (sea foam). I am still experiencing the same problem. The engine is 5.7 V8 TBI. Exhaust appears clean.

I dont have any testing equip and I cant afford dealer labor costs.

Any ideas?
Sep 15, 2010 at 7:53 AM
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WRENCHTECH
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First thing I would check is remove the EGR valve and see if it is closing all the way. Also try driving it disconnected although this will set a trouble code that will have to be cleared after.
Also clean the throttle body thoroughly.
Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle.
Sep 15, 2010 at 8:09 AM