Engine - Rough Idle Cold or Hesitation
90chevy05GMC NUMBER: 90-6E-41
GROUP: 6D Engine Emission
DATE: March, 1990
CORPORATE
NUMBER: 036501
SUBJECT: ROUGH IDLE COLD/HESITATION (NEW CALIBRATION PROM AND STARTING PROCEDURE)
MODELS: 1990 C3, K3, R2, R3, G3, P3, V3 WITH 7.4L
Condition:
Owners of some 1990 C, F, 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 (M40) 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 stin 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, fohow the procedure as outhned above, except depress and hold accelerator pedal V4 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