ROUGH IDLE, CHUGGLE, LOW SPEED NEW PROM P/N'S

VEHICLES AFFECTED: 1986 'F' CARS WITH LB9 TPI ENGINE (ENGINE CODE F)

New service calibrators (Ref: Called Mem-Cal In Shop Manual) have been released for the 1986 'F' car with the 5.01 TPI engine. These new calibrators will address the following customer comments:

1. "Rough Idle" on both hot and cold engine - the idle speed is raised to 650 plus or minus 50 RPM.

2. "Chuggle or Shudder" at low speeds - torque converter, clutch (TCC) engagement speed is raised to 41 MPH.

3. "Hesitation" on light acceleration with a hot engine.

4. "Cold Driveability" - New calibration eliminates light sag and potential backfire on cold driveaway.

5. "Service Engine Soon" Lights - Eliminates the following false Codes:

A. Code 32 - EGR System Failure B. Code 33 - Mass Airflow Sensor Voltage High C. Code 34 - Mass Airflow Sensor Voltage Low D. Code 43 - Electronic Spark Control E. Code 44 - Lean Exhaust Indication

If normal engine diagnostics and repair do not correct the above conditions, it will be necessary to replace the calibrator in the ECM. Below is a listing of the new calibrators and their usages.

ON AIR CONDITIONING (C-60) 'F' CARS

With QYZ (P215/65 R 15/N 15" Tire) Use 1228290 Calibrator With QAC (P235/60 VR 15N Tire) Use 1228291 Calibrator With QDZ (P245/50 VR 16N Tire) Use 1228291 Calibrator

ON NON-AIR CONDITIONING (C-41) 'F' CARS

With QYZ (P215/65 R 15/N 15" Tire) Use 1228292 Calibrator With QAC (P235/60 VR 15N Tire) Use 1228293 Calibrator With QDZ (P245/50 VR 16N Tire) Use 1228293 Calibrator

Use Applicable Labor Time and Operation Numbers.

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.