Engine - Intermittent Increase in Idle RPM
Group Ref.: Engine Fuel & EmissionBulletin No.: 476505
Date: February, 1994
SUBJECT:
INTERMITTENT INCREASE IN ENGINE IDLE RPM; INITIAL ENGINE START/STALL AND/OR SAG/HESITATION ON DRIVE AWAY FOR AUTOMATIC TRANSMISSION EQUIPPED VEHICLES (NEW "FLASH" PROM)
MODELS:
1994 CHEVROLET CAMARO
1994 PONTIAC FIREBIRD WITH 3.4L ENGINE (VIN S - RPO L32)
CONDITION:
Some owners may experience two different driveability conditions. These conditions can be addressed with the use of the same new "Flash" PROM.
1. An intermittent increase in engine idle RPM.
2. Vehicles equipped with an automatic transmission may experience "cold start stall," "hesitations," and/or "sag."
CAUSE:
There are two causes, depending on the condition being addressed.
1. A non-zero throttle position (TP) sensor reading during a closed throttle condition may cause an intermittent increase in engine idle RPM.
2. Variability in the volatility of commercially available fuels may cause the air fuel ratio to be too lean upon cold engine starts.
CORRECTION:
A new "Flash" PROM is available to correct both conditions.
1. This new PROM has enhanced software to eliminate a non-zero TP sensor reading during a closed throttle condition.
2. A calibration change was made to the automatic transmission equipped calibration to diminish "cold start stalls," "hesitations," and/or "sags."
No other driveability issues are addressed with this "Flash" PROM.
Vehicles built after the vehicle identification numbers below will have this calibration already installed by the vehicle assembly plant.
PARTS INFORMATION:
The new "Flash" PROM will be available on the January 1994 CD released by STG. Part numbers are as follows (see illustration).
WARRANTY INFORMATION:
For vehicles repaired under warranty, use:
Labor Operation: T0500
Labor Time: 0.3 hour