DETONATION/EXHAUST ODOR INSTALL NEW PROM. Chevrolet Chevy C Pickup

Subject: DETONATION AND/OR EXHAUST ODOR

Model and Year: 1990 C/K, R/V, G AND P TRUCK WITH 7.4L ENGINE

Condition: Some owners of 1990 trucks with the 7.4L engine may comment of either detonation at highway speeds or exhaust odor (sulfur smell) at idle.

Cause: The original spark advance and idle calibration may generate detonation or sulfur odor comments for a few isolated conditions.

Correction: On trucks where these conditions can not be repaired using normal service procedures, a revised calibration PROM should be installed (See below).

Part Emission PROM SCANNER Number System Trans. Broadcast I. D. -------- ---------- ---------- --------- --------- 16165446 NA4 (above M40 (Auto) AYKK 5451 8600 GVW)

16165447 NA4 (above M20 (Manual) AYKL 5461 8600 GVW)

Parts are expected to be available on June 3, 1991. Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be cancelled as incorrectly ordered while the 400 control is in place.

Note: These PROMs SHOULD NOT BE USED on the Chevy "S.S."

Labor Operation Number: T0500

Labor Time : .6 Hour

Trouble Code: 92

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.