1992 - 1996 Corvette: Service Bulletin: Engine Miss/Poor Driveability Symptoms

Subject: Engine Miss/Poor Driveability Symptoms (Install Opti-Spark (ABITS) Distributor Assembly Service Kit)
Model and Year:
1994-96 Buick Roadmaster
1994-96 Cadillac Fleetwood
1992-96 Chevrolet Corvette
1993-97 Chevrolet Camaro
1994-96 Chevrolet Caprice
1993-97 Pontiac Firebird/Trans Am
with 4.3L or 5.7L Engines (VINs W, P, 5 -- RPOs L99, LT1, LT4)
Source: Chevrolet Dealer Service Bulletin
Bulletin Number: 87-65-27

THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 90-416-8E, DATED APRIL 1991. WARRANTY INFORMATION HAS BEEN ADDED. ALL COPIES OF 90-416-8E SHOULD BE DISCARDED.

CONDITION:

Some vehicles with the above engines and equipped with the Opti-Spark (ABITS) ignition system may exhibit an engine miss and/or poor driveability symptoms.

CAUSE:

The (ABITS) cap and the rotor may show carbon tracking, cracking, or water intrusion which can cause an engine miss and/or poor driveability symptoms.

CORRECTION:

Perform strategy-based diagnosis. If it is determined that the ABITS cap and/or rotor is the source of the concern, then a service kit may be now implemented instead of a complete ABITS assembly.

PARTS INFORMATION:

There are two (2) variations of Opti-Spark Distributors. It will be mandatory to identify which type is to be serviced for proper parts procurement.

• The Opti-Spark Distributor II (Pin Drive -- WITH positive vent system) can be identified by the intake manifold vacuum hose connection (3), the air intake duct hose connection (4), or the non-splined pin drive (1). Refer to Figure 1.
  
  
• The Opti-Spark Distributor I (Splined Drive -- WITHOUT positive vent system) can be identified by the splined pin drive (1) or the lack of an intake air vacuum hose connection and an air intake duct hose connection. Refer to Figure 2.

Important

It is necessary to use tool J 39997 (or the equivalent) for the distributor cap screws and tool J 39998 (or the equivalent) for the rotor screws.