PISTON SCUFFING - 3.1L ENGINE REPL PARTIAL ENG. (NOT PISTON)

Subject: PISTON SCUFFING - 3.1L ENGINE REPLACE A PARTIAL ENGINE (NOT PISTON)

Models Affected: 1990 TRANS SPORT MODELS WITH 3. 1L ENGINE

This bulletin cancels and replaces bulletin 90-6-52A and 91-6-52. By deleting the 1991 models, this bulletin had to be made into a 1990 bulletin, deleting 91-6-52. Please discard bulletin 90-6-52A and replace it with 90-6-52B. The text of the bulletin has not changed.

Condition: Some Trans Sport models may exhibit engine piston scuffing, which could result in cold engine knock at low ambient temperatures. This condition will not lead to engine failure and is limited to cylinders #2, #4 and #6.

Cause: Premature wear of the pistons due to low adhesion of the tin plating.

Correction: If pistons need replacement due to scuffing, a partial engine replacement is HIGHLY recommended rather than replacement of individual pistons. This recommendation is made since other pistons in these engines might have to be replaced later.

Labor Operation Number: J 1820

Labor Time: Use applicable time

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.