Engine - Hard Start/Detonation When Hot
88pontiac07Bulletin Number: 88-6-34
Reference Number: 836304R
Publish Date: 4/88
HARD START (LONG CRANKING TIME/ENGINE Subject: FAILS TO RUN) WHEN HOT AND/OR DETONATION (SPARK KNOCK)
Models 1987-88 6000 AND FIERO CARS WITH 2.5L
Affected: 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.