S10/T10 Blazer 4WD V6-262 4.3L (1989)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
Engine - Rough Idle/Stall After Cold Start
Number:
91-44-6E
Section:
6E
Date:
August 1990
Corp. Bulletin No.: 036511
Subject:
ROUGH IDLE/STALL AFTER COLD START
Model and Year: 1988-91 S/T TRUCKS WITH 4.3L (VIN CODE Z) ENGINE AND AUTOMATIC TRANSMISSION 4L60
TO:
ALL CHEVROLET DEALERS
APPLICATION:
1988-91 4.3L Auto. S/T Truck W / Calif. Emission (NB2) 1988-90 4.3L Auto. S/T Truck W / Federal Emission (NA5)
CONDITION:
Some of the above trucks may exhibit a rough idle, sag or stalling condition after cold start-up at intermediate ambient
temperatures of 30-70 degrees F. This condition may be most noticeable while performing a Park to Drive/Reverse shift. The
condition improves as the engine reaches normal operating temperature.
CAUSE:
The condition is due to low idle speeds and/or lean air/fuel ratios after cold start-up.
CORRECTION:
To correct this condition install a new service calibration PROM which revises warm-up idle speeds. The new PROM will
also raise the normal controlled idle speed from 500 RPM to 525 RPM in drive. Reference the chart below for the proper
PROM application.
Note:
These PROMs were released to production as follows: The Federal PROM is in all 1991 models. The California PROM will go into
production in August 1990 for 1991 models.
Parts are currently available from GMSPO.
Labor Operation:
T0500
Labor Time:
0.8 Hrs.