Engine - Bump Sensation When Decelerating: Overview

9209pontiac01

Bulletin Number: 91-6-58
Reference Number: 136526
Publish Date: 1/92


Subject: CLUTCH "BUMP" WITH 3.4L (VIN CODE X) AND MANUAL TRANSMISSION (ADD SWITCH AND REPLACE MEMCAL)

Models
Affected: 1991 GRAND PRIX MODELS


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:

It will be necessary to replace the following parts to correct this condition.