ENGINE SPARK KNOCK, SURGE AND/ OR HIGH COLD IDLE SPEED NEW PR

SUBJECT: ENGINE SPARK KNOCK, SURGE AND/OR HIGH COLD IDLE SPEED (NEW PROM)

MODELS: 1990-93 S TRUCKS W/2.8L (LL2) ENGINE AND MANUAL TRANSMISSION

CONDITION

Some owners of 1990-93 S-15 pickup trucks with a 2.8L engine (RPO LL2) and manual transmission may comment that they encounter engine spark knock, surge, or high cold engine idle speed.

CAUSE

Engine system/component variability.

CORRECTION

If any of the subject conditions are found, then use the following procedure:

1. Perform diagnostic, per Section 6E of the Service Manual. Make any adjustments that are required, or replace any inoperative parts.

2. If no other conditions are found using normal diagnostics, and this condition or conditions still exist, then replace the prom.

SERVICE PARTS INFORMATION

P/N Description Code --- ----------- ---- 16171720 Prom (3.42 and 3.73 AXIL) AZUU

16171758 Prom (4.11 Axle) AZUW

Parts are currently available from GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty, use:

Labor Op Labor Time -------- ---------- T-0500 0.8 Hr.

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.