ROUGH IDLE,COLD/HESITATE (NEW CALIB. PROM & START PROCEDURE)

MODELS: 1990 C3, K3, R2, R3, G3, P3, V3 WITH 7.4L

Condition:

Owners of some 1990 C, K, R, V, G, and P trucks with a 7.4L engine may comment about rough idle cold or hesitation.

Cause:

Either of these conditions may be the result of calibration and/or current starting procedure.

Correction:

For trucks above 8500 lbs GVW a new calibration PROM is available. For correct usage see chart below.

NEW NEW NEW PROM BROADCAST SCAN TRANSMISSION KIT NUMBER CODE TOOL I.D. ------------ ----------- ---- --------- 3-Spd Auto (M-40) 16151512 AUMZ 1331 4-Spd Manual (M-20) 16151516 AUNA 1341

Parts are currently available from GMSPO.

For all 7.4L trucks the starting procedure (cold or hot engine) is as follows:

Do not depress the accelerator pedal. With your foot off the pedal, crank the engine for 3 seconds. If the engine does not start in 3 seconds, push the accelerator pedal to 1/4 throttle for the remainder of the 15 seconds. If the engine does not start, wait 15 seconds to let the starter cool down. Then crank the engine at wide-open throttle for a maximum of 10 seconds. If the engine still does not start, wait another 15 seconds and repeat the entire procedure. Release the key and accelerator pedal when the engine starts.

New 7.4L Cold Starting Procedure

At ambient temperatures of less than 60 degrees Fahrenheit, follow the procedure as outlined above, except depress and hold accelerator pedal 1/4 down for about 2 seconds after engine has started.

Use Labor Operation Number: T0500

Use Labor Time: .6 hr. for C/K/R/V/P models .7 hr. for G models

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.