ENGINE DETONATION KNOCK SENSOR AND NEW PROM

ENGINE DETONATION ON 5.0L L69 ENGINE

Model and Year: 1984 MONTE CARLO SS

TO: ALL CHEVROLET DEALERS

Customer comments of engine detonation may be received on 1984 Monte Carlo super sport vehicles equipped with 5.0L L69 engines. Some audible detonation is common on vehicles equipped with knock sensor systems and can be expected when engines are cold, since the ESC system does not start functioning until the engine warms up. For vehicles that exhibit excessive or abnormal warmed up detonation, the following procedures are recommended:

1. Check and verify engine timing is set to specification.

2. Remove knock sensor, checking torque required to remove it. If removal torque is in excess of 30 ft. lbs., install a new sensor.

3. Check the removed sensor to make sure it is not distorted, bent, or damaged.

4. Wire brush the threads on the sensor and clean the threads in the engine block thoroughly.

5. Before reinstalling sensor, the threads must be painted with a sealer (GM P/N 9985000). The sensor should be installed to 12-16 ft. lbs.

In the event the above action does not correct the complaint, a service PROM with revised spark calibrations has been released. Refer to the following chart for correct usage:

New P/N Usage ------- ----- 1227178 1984 Federal L69 With 3-Speed Automatic 1227179 1984 California L69 With 3-Speed Automatic

Initial timing in all cases (before and after) is 6 degrees BTDC.

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.