Engine - Excessive Spark Knock at Part Throttle
86chevy13Number: 86-79
Section: 6
Date: MAY, 1986
Subject: INOPERATIVE EGR VALVES
Model and Year: 1986 CELEBRITY, CAMARO, S/T TRUCKS AND "M" VANS WITH 2.5L L4 ENGINE (VIN CODES R, 2, E)
TO: ALL CHEVROLET DEALERS
Some 1986 vehicles with a 2.5L L4 engine may exhibit excessive spark knock, at part throttle, due to an inoperative EGR valve.
If an EGR valve has been diagnosed as inoperative because it does not respond to a normal vacuum signal, remove the vacuum hose and check the orifice in the vacuum fitting for a plugged condition. The orifice may have excessive, hardened, hose assembly lubricant blocking it. If this condition exists, clear the orifice with a small wire, or pin, return the vacuum hose to the fitting and test the EGR valve for function.
If the EGR is still inoperative, replace it.
Use applicable labor operation number and labor time.