EXCESSIVE SPARK KNOCK -PING INOPERATIVE EGR VALVE

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.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.