Engine Controls - Detonation (Spark Knock)

83-152
6E

MAY, 1985
Subject: DETONATION (SPARK KNOCK)
Model and Year: 1983 CAVALIERS EQUIPPED WITH 2.0L ENGINE (VIN CODE P)
TO: ALL CHEVROLET DEALERS
This cancels and supersedes information contained in Chevrolet Dealer Service Bulletin 83-148 dated February, 1985. This copy identifies an additional PROM application.

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 3.)
3. If timing and EGR system checks are satisfactory.

A. On manual transmission vehicles:

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

B. On automatic transmission vehicles:

^ Install PROM package:

- With Federal emissions and without Cold Startability Revision (reference Chevrolet Dealer Service Bulletin 84-221), P/N 1226823.

- With Federal emissions and with Cold Startability Revision (reference Chevrolet Dealer Service Bulletin 84-221), P/N 1227253.
- 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.