Engine - Surge/Abrupt 3-2 Downshift

88pontiac01
Bulletin Number: 88-6-19
Reference Number: 836507
Publish Date: 1/88
Subject: DRIVEABILITY - EGR SURGE AND ABRUPT 3-2 DOWNSHIFT

Models

1988 2.0L OVERHEAD CAM L-4 ENGINE

Affected: (VIN CODE M) IN SUNBIRD AND GRAND AM MODELS WITH AUTOMATIC TRANSMISSION
Some early built 1988 Sunbird and Grand Am vehicles with the L-4 turbo engine may demonstrate one or both of the following driveability conditions:

1. Exhaust Gas Recirculation (EGR) Induced Surge

Light surge at road load driving conditions (approximately 40 mph) with a warmed-up engine. Disconnecting the EGR valve and plugging off the vacuum line will verify EGR induced surge.

2. Abrupt 3-2 Downshift

During a passing maneuver in the 40-55 mph speed range, a potentially harsh 3-2 downshift prior to normal torque converter clutch (TCC) unlock may occur. Other automatic transmission conditions (if present) should be corrected prior to any final verification of the above condition.

These conditions can be repaired by changing the ECM calibration PROM. Using a TECH 1 scanner, the original ECM part numbers can be verified.

PART NUMBER
PROM ASSEMBLY Vehicles Built With ECM P/N 1608"4262"

16120036 Pontiac Sunbird and Grand Am

Use applicable Labor Time and Operation Number.