Engine - Detonation (Spark Knock)

Subject: DETONATION (SPARK KNOCK)


Model and Year: 1983 CAVALIERS EQUIPPED WITH 2.OL ENGINE
Number: 83-148


Subject: 6E (VIT)

Date: Feb., 1985

EFI DIAGNOSTIC CHART:

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

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

2. Check for proper EGR per chart (see Page 2).

3. If timing and EGR system checks are satisfactory.

A. On Manual Transmission Vehicles:

^ Retard base timing to 4~ ATDC.
^ Install tune-up label.

B. On Automatic Transmission Vehicles:

^ Install PROM package:

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

^ Set base timing to 6~ BTDC.

^ Install tune-up label that is included in PROM package.


Use applicable labor operation.