1999 Pontiac Grand Prix GTP Problems

RepairPal has identified the most common problems with the 1999 Pontiac Grand Prix GTP as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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Known Problems

The mass air flow or crankshaft position sensor may fail causing the engine to intermittently stall. It may be necessary for the engine to cool down before it will restart.

The intake manifold gasket may develop and external engine oil or coolant leak. In some cases, an internal coolant leak may occur causing coolant to mix with the engine oil. Running the engine with a coolant/oil mix may result in engine damage. Replacing the intake manifold gasket should correct this issue.

You may be able to prevent transmission problems by servicing the transmission and inspecting the fluid every 30,000 miles. If the fluid is dark or burned then the transmission system should be completely flushed.

The water pump may develop a coolant leak resulting in an engine overheating condition.

The fuel pump may fail causing engine to stall and not restart.

The supercharger may develop a noise in the front section of the supercharger assembly. The is due to a worn coupler. Our technicians tell us that a remanufactured coupler section is available from aftermarket suppliers.

The automatic transmission shifter may fail, or a wire may break near the shifter causing the ignition key to become stuck in the ignition lock cylinder.

The serpentine belt tensioner pulley may wear out. Our technicians tell us that in order to get a new pulley from General Motors you must purchase a complete belt tensioner assembly.

The crankshaft position sensor, ignition module, and/or powertrain control module (PCM) may fail resulting in illumination of the Check Engine Light with ignition system related fault codes stored in the PCM. Patience is necessary when dealing with this specific situation as normal diagnostic procedures are not effective. In many cases, the best option is to replace parts, one at a time until the fault is corrected.

An automatic transmission fluid leak may develop from the rubber section of a transmission cooler line. In some cases the rubber section of hose can be replaced. In others, the complete cooler line must be replaced to correct this type of leak.

The EGR tube may develop an engine vacuum leak causing the Check Engine (SES) light to illuminate.

The battery may leak acid at the battery cable connections. As a result corrosion may form on the battery cable ends. Leaking batteries should be replaced and the cables need to be thoroughly cleaned or replaced if necessary.

The intake manifold gasket may develop external engine oil leak. The manifold gasket will need to be replaced to correct this issue. RepairPal cannot confirm a recall for this concern on these models.

Extended life coolant may become contaminated and require cooling system service before the recommended 100,000 miles.

Corrosion may develop at the connection between the ignition coil tower and spark plug wire resulting in an engine misfire. The Ignition coil and spark plug wire should both be replaced to correct this condition.