Engine - Idle Shake?Detonation

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Model Year 1982

Bulletin No. 82-T-90

File In Group 64A

Number 29

Date July, 82
SUBJECT: Idle Shake - Revised Service PROM Calibration

MODELS AFFECTED: 1982 Centry and Skylarks
Equipped with 2.5L EFI And Automatic Transaxle


A new PROM has recently been released with revised spark timing calculations and slightly increased idle speeds.

The change in spark timing was made to eliminate any detonation under moderate acceleration at cruising speeds (40-55 mph). The increased idle speed will reduce vibration or shake at idle speeds.

The service part number for this new PROM is 1226169 (Broadcast Code 0262-AOS). This PROM is to be used only on 1982 Centurys and Skylarks with the 2.5L, EFI, automatic transaxle, and first design (3-board) ECM. The second design (2-board) ECM has the spark revision already incorporated in its PROM.

PROM's should be replaced only as required to correct the above conditions.