M/T - Bump Sensation When Decelerating: Overview

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Number: 91-472-7C

Section: 7C

Date: JAN 1992

Corporate Bulletin No.: 136526

ASE No.: A3


Subject: CLUTCH BUMP


Model and Year: 1991 LUMINA WITH 3.4L ENGINE AND MANUAL TRANSMISSION


Condition:

The customer may comment that the manual transmission has a "bump" sensation when decelerating. The engine may decelerate too quickly if the driver lets up on the accelerator before depressing the clutch, causing a momentary "bump" sensation just before the clutch is fully released.

Cause:

There is no "clutch anticipate" signal to the ECM to allow for less abrupt fuel cutoff to the injectors during shifting.

Correction: