DETONATION/SPARK KNOCK NEW PROM AND TUNE-UP LABEL

Models Affected: 1983 Skyhawks Equipped with 2.0L Engine (Vin Code P)

NOTICE: This bulletin supersedes Bulletin 85-6E-5 dated Mar. '85. Please discard bulletin 85-6E-5 and replace it with this one, 85-6E-5A.

This bulletin should be used when detonation (spark knock) is encountered on some 1983 Skyhawks. It should be noted that "burst" detonation (very short period following a quick throttle movement) is considered acceptable.

1. Check base timing 0 DEG (by-pass disconnected).

2. Check for proper EGR per chart (Figure 1).

3. If timing and EGR system checks are satisfactory.

A. On Manual Transmission Vehicles:

Retard base timing to 4 DEG ATDC. Install tune-up label, P/N 14086563.

B. On Autcmatic Transmission Vehicles:

Install PROM package:

- With Federal emissions - P/N 1226823. - With California emissions - P/N 1226984.

Set base timing to 6 DEG BTDC. Install tune-up label that is included in PROM packge.

Use applicable labor operation.

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.