Engine - Spark Knock at Part Throttle
Number 86-6 (Gasoline) - 44 Date 6/86Subject: SPARK KNOCK 1986 2.5L-L4 ENGINES
1986 6000, FIREBIRD, GRAND AM, AND FIERO MODELS WITH 2.5L-L4 ENGINE; (VIN CODES R, U, AND 2)
Some 1986 vehicles with a 2.5L-L4 engine may exhibit spark knock, at part throttle, due to an inactive EGR valve.
If diagnosis indicates the EGR valve does not respond to a normal vacuum signal, remove the vacuum hose and check the orifice in the EGR vacuum fitting for a restricted condition. The orifice may contain excessive, hardened, hose assembly lubricant. If this condition exists, clear the orifice with a small wire, or pin, return the vacuum hose to the fitting and retest the EGR valve for proper function.
If the EGR does not function properly during retest, replace it.
Use applicable labor operation number and labor time.