HARD START, DETONATION OR STALL WHEN HOT. Pontiac Fiero 1988

1987-88 6000 AND FIERO CARS WITH 2.5L ENGINE (VIN CODE R) AND 1987 GRAND AM CARS WITH 2.5L ENGINE (VIN CODE U)

Some of the above 1987 and 1988 vehicles equipped with the 2.5L engine may experience two driveability conditions. The conditions are (1) extended cranking times/engine fails to run when the engine is hot and (2) spark knock (detonation).

The repairs outlined in this bulletin should be made only if standard diagnostics outlined in the service manual do not correct the discrepancy.

SPARK KNOCK (DETONATION)

An ECM calibration change is available to retard the spark advance when the engine is operating in moderate load conditions between 1800 and 2800 engine RPM. An example of this condition is spark knock observed while negotiating a moderate grade when cruising at 55-65 mph. The service PROMS listed in Table #2 should be installed to correct this condition.

Labor Operation Number: T1316

Labor Time : .4 Hours

HOT ENGINE STARTABILITY (Long Cranking Time/Stalling When Hot) ----------------------- Conditions experienced when starting a hot engine, such as extended cranking times/engine fails to run can be repaired by installing the components shown in Table #1. The conditions may be caused by vaporizing of the fuel in the fuel lines and throttle body injector assembly (TBIA) under hot conditions.

NOTICE: IT IS MANDATORY TO CHANGE THE ECM CALIBRATION PROM IN CONJUNCTION WITH THE FUEL PUMP.

The fuel pumps listed in Table #1 deliver far more fuel at low system voltages than the original fuel pump and will result in irregularities when starting the engine in cold weather. To avoid these irregularities, the ECM PROMS must be changed along with the fuel pump. Instructions detailing assembly of the fuel pump, fuel sender, and pulsator are included with the fuel pump.

In an effort to reduce the service packages, the spark advance retard has been incorporated into this prom calibration. This calibration will correct the hot engine starting irregularities with no observed change in powertrain performance because of the spark advance retard change.

Labor Operation Number: T1314

Labor Time for the following Car Lines: 6000 Grand Am Fiero --------------------------------

1.6 Hr. 1.7 Hr. 1.4 Hr.

HOT ENGINE STARTABILITY AND SPARK KNOCK

The combination of these irregularities can be corrected by installing the components listed in Table 1.

Labor Operation Number: T1315 Labor Time for the following Car Lines: 6000 Grand Am Fiero --------------------------------- 1.6 Hr. 1.7 Hr. 1.4 Hr.

Table 1

Vehicle Configuration

Rubber Fuel Model Bumper Sender Carline Year Trans. Cluster Part No. Pkg. p/n ------- ---- ------ ------- ---------- ---------

6000 87 Auto. Digital 25004553 25093744

6000 87 Auto. Analog 25004553 25093744

6000 88 Auto. Analog 25004553 25093744

Fiero 87 Auto. Analog 25004553 25093526

Fiero 87 Man. Analog 25004553 25093526

Fiero 88 Auto. Analog 25004553 25093526

Fiero 88 Man. Analog 25004553 25093526

Grand Am 87 Auto. Analog 25004553 25092778

Grand Am 87 Man. Analog 2500453 25092778

Required Parts

Pulsator Fuel Pump ECM Prom Package Package Package Carline Year Part No. Part No. Part No. ------- ---- -------- -------- ---------

6000 87 25094266 25115764 16121210

6000 88 25094266 25115764 16121515

Fiero 87 25094266 25115764 16121513

Fiero 87 25094266 25115764 16121514

Fiero 88 25094266 25115764 16121513

Fiero 88 25094266 25115764 16121514

Grand Am 87 25094266 25115925 16121217

Grand Am 87 25094266 25115925 16121218

TABLE 2

VEHICLE CONFIGURATION REQUIRED SERVICE PROM --------------------- ----------------------

CARLINE MODEL YEAR TRANSMISSION PART NUMBER

6000 87 AUTOMATIC 16122665

6000 88 AUTOMATIC 16122667

FIERO 87/88 AUTOMATIC 16122663

FIERO 87/88 MANUAL 16122664

GRAND AM 87 AUTOMATIC 16121266

GRAND AM 87 MANUAL 16121267

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.