ENGINE INTERMITTENT STALLING NEW PROM PART NUMBER
VEHICLES AFFECTED: SOME 1986 AB, CB, EB, HB EQUIPPED WITH 3.8L SFI ENGINES (VIN CODES 3 AND B)
AB = A SERIES EB - E SERIES CB = C SERIES HB = H SERIES
Notice: This bulletin supersedes PSB 86-638-126 dated December 22, 1986.
Some 1986 vehicles equipped with 3.8L SFI engines (VIN Codes 3 and B) may experience an intermittent condition where the engine may occasionally not stay running on deceleration or during parking lot maneuvers under closed throttle conditions.
If this condition is experienced on a vehicle when the basic engine, controls and systems are performing properly, and cannot be repaired by using currently published service and diagnostic procedures, it may be necessary to install a new service PROM which replaces the obsolete sensor kit.
Effective with publication of this bulletin, the four components involved in Service Kits 25531123 through 25531129, referenced in PSB 86-638-126 should only be replaced individually as necessary, and Labour Operation Number T5123 will be invalid.
All sensor kits currently existing in dealership inventories should be disassembled and the parts returned to dealer stock and used for service replacements.
Listed below are the revised service procedures and service PROM part numbers for an intermittently "won't stay running" condition:
1. After it has been determined that the basic engine, engine controls and systems are performing properly, replace the PROM.
2. Remove the air intake duct from the throttle body. Clean the PCV residue from the throttle body bore in the area behind the throttle plate, using a shop towel with "GM Top Engine Cleaner" (Part Number 992872) or "AC-Delco Carburetor Tune-Up Conditioner" (Part Number X66-P) or equivalent product that doesn't contain methyl ethyl ketone. It should be noted that what appears to be just a small amount of PCV residue accumulation can be enough to limit air flow, and result in an inaccurate minimum air rate adjustment.
3. Reinstall the air intake duct and check the minimum air rate and adjust, if necessary, to 500 RPM using the following procedure:
a) After the engine has reached normal operating temperature, turn the engine off and ground the diagnostic test terminals of the ALDL connector.
b) Turn on the ignition, but do not start the engine. Wait at least 30 seconds.
c) With the ignition "ON", disconnect the IAC motor electrical connector.
d) Remove the ground from the ALDL connector and start the engine.
e) If necessary, remove the cap from adjusting screw and adjust engine to 500 RPM while vehicle is in drive and A/C is off.
f) Turn ignition "Off" and reconnect connector at IAC motor.
4. Adjust throttle position sensor to .40 - .44 bolts. DO NOT EXCEED .44 VOLTS.
SERVICE PROM PART NUMBERS
AXLE SALES CODE MODEL I.D. LOCATED ON SCANNER PROM I.D. IF SERVICE APPLICATION AXLE DECK LID DECAL THIS PROM IS INSTALLED PART NO.
AB All N/A 8591 1228591 CB All N/A 8592 1228592 Electra T-Type All N/A 8593 1228593 HB 2.84 F17 8594 1228594 HB 2.73 FP3 8595 1228595 EB All N/A 8620 1228620 Riviera T-Type All N/A 8621 1228621
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.
