1. Gather More Information:
* When does it shut off? Does it happen only when idling, accelerating, turning, or under specific conditions (hot engine, cold engine, etc.)? The conditions under which the car stalls are crucial clues.
* Does the engine crank when it stalls? If it cranks but doesn't start, it points to a different problem than if it just completely dies and won't crank at all.
* Check the gauges: Before, during, and after a stall, observe the fuel gauge, battery voltage gauge (if equipped), and engine temperature gauge. Any anomalies could provide hints.
* Any warning lights? Note any warning lights (check engine, battery, etc.) that illuminate before, during, or after the stalling.
* Smell anything unusual? A strong smell of fuel or burning might indicate a fuel system or electrical issue.
2. Potential Problem Areas (Beyond Simple Wiring):
* Crankshaft Position Sensor (CKP): This sensor is critical for the engine's timing. A faulty CKP can cause the engine to stall intermittently. This is a common culprit in many vehicles exhibiting these symptoms.
* Cam Position Sensor (CMP): Similar to the CKP, a faulty CMP sensor can lead to erratic engine behavior and stalling.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A malfunctioning MAF can cause the engine to run lean or rich, leading to stalling.
* Fuel Pump: A failing fuel pump might not deliver enough fuel under certain conditions, causing the engine to stall. Listen carefully for the fuel pump whirring when you turn the key to the "on" position (before cranking). A weak or intermittent whirring could indicate a problem.
* Ignition System: While you've replaced wires, other ignition components like the ignition coil, ignition module, or distributor (if equipped) could be faulty.
* Alternator: A failing alternator might not charge the battery properly. If the battery voltage drops too low, the engine can stall.
* Computer/ECU: While less likely, a problem with the engine control unit (ECU) could be causing the intermittent stalling. This usually requires specialized diagnostic tools to check.
* Grounds: Poor electrical grounds can cause all sorts of intermittent electrical problems. Check all major grounds to make sure they are clean and secure.
* Fuel filter: A clogged fuel filter can restrict fuel flow.
3. Next Steps:
* Get a second (or third) opinion: Find a reputable mechanic who specializes in older vehicles or has experience with Pontiacs. Explain all the symptoms and details you've gathered.
* Diagnostic scan: A thorough diagnostic scan using a professional-grade scan tool is essential. It can read trouble codes from the ECU that might pinpoint the problem. A simple code reader from an auto parts store may not be sufficient.
* Consider a fuel pressure test: This test will measure the fuel pressure in the fuel rail to check if the fuel pump and fuel system are delivering adequate fuel.
* Check for vacuum leaks: A vacuum leak can cause erratic engine operation.
Important Note: Continuing to drive the car with this intermittent stalling issue could cause further damage or even lead to a dangerous situation. It's best to limit driving until the problem is diagnosed and repaired.
