S15/T15 2WD Jimmy V6-262 4.3L (1991)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
Engine - Rough Idle/Stall After Start Up
GMC NUMBER:
91-6E-17
GROUP:
6E ENGINE EMISSIONS
DATE:
SEPTEMBER, 1990
CORPORATE
NUMBER:
036511
SUBJECT:
ROUGH IDLE/STALL AFTER COLD START
MODELS:
1988-91 S/T TRUCK W/4.3L AND AUTOMATIC TRANSMISSION (4L60)
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 condi-
tion 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.
SERVICE PARTS INFORMATION
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 productlon
in August, 1990 for 1991 models. Parts are currently available from GMSPO.
WARRANTY INFORMATION
Labor Operation:
T0500
Labor Time:
0.8 hr.
NOTE:
Labor Operation is coded to base vehicle coverage in the warranty system.
