Engine Controls - Idle Surge on Cold Start
File In Section: 6E- Engine Fuel & EmissionBulletin No.: 67-65-31A
Date: November, 1996
Subject:
Idle Surge on Cold Start
(New Flash Prom)
Models:
1996 Buick Century
1996 Oldsmobile Ciera
with 3100 V6 Engine (VIN M - RPO L82)
This bulletin is being revised to correct labor op under warranty information. Please discard Corporate Bulletin Number 67-65-31 (Section 6E - Engine Fuel and Emission).
Condition
Some owners may comment that the engine idle will fluctuate on the initial cold start of the day prior to the vehicle being shifted out of Park position. This typically occurs at the point the emission control system goes from "open" loop to "closed loop" status. This condition is most noticeable in warmer ambient temperatures.
Cause
The idle surge is caused by the difference in fueling between "open" and "closed" loop operation.
Correction
A new flash prom has been released to correct this condition. The following changes have been incorporated in the new flash prom:
1. Time delay increase to closed loop.
2. Smaller fueling corrections in the transition from open to closed loop.
These changes serve to take smaller fueling corrections from open to closed loop to avoid idle.
Parts Information
The new flash prom will be available from the GM Service Technology Group starting with CD # 16.
Important:
Do not attempt to order the flash proms from GMSPO. The flash proms are programmed into the PCM (Powertrain Control Module) via a Techline Tool device.
Emission Calibration Number
Nationwide 16251204
Canadian 16251214
Warranty Information
For vehicles repaired under warranty, use as shown.