* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the engine's rotational position. A failing CKP sensor can cause intermittent stalling because it might lose signal briefly, then regain it. This is a very common cause of this type of problem in older vehicles.
* Cam Position Sensor (CMP Sensor): Similar to the CKP sensor, but for the camshaft. A faulty CMP sensor can also lead to the same symptoms.
* Ignition Coil(s): A failing ignition coil can intermittently fail to provide the spark needed for combustion. This can be particularly problematic if only one coil is failing intermittently. Roadmasters often have multiple coils.
* Distributor (if equipped): While less common on a '92 Roadmaster, if it still uses a distributor, problems within it (like worn points or a failing pickup coil) could produce the same effect.
* Fuel Pump Relay: A relay is an electrical switch. A failing fuel pump relay might intermittently stop power to the fuel pump, leading to stalling. This will usually mean the pump doesn't even "whine" when the key is turned.
* Mass Air Flow (MAF) Sensor: A dirty or failing MAF sensor can disrupt the air/fuel mixture, causing the engine to stall, especially under load. However, it's less likely to cause an instant stall and restart.
* Intermittent Wiring Issue: A corroded, loose, or damaged wire anywhere in the ignition or fuel system could cause the exact symptoms described. Look closely at connectors near the engine and under the hood.
* Fuel Pump: While less likely to cause an immediate stall and restart *without* a warning sign (like sputtering), a very weak fuel pump could be barely delivering enough fuel, and if the engine demand increases momentarily (like climbing a hill) it could starve the engine and cause a stall.
Troubleshooting Steps:
1. Check the obvious: Look for any loose or corroded connections in the engine bay, paying close attention to the ignition system, fuel system, and sensors.
2. Check engine codes: Use an OBD-I scanner (appropriate for that year) to read any stored diagnostic trouble codes (DTCs). This will likely provide significant clues.
3. Test the CKP and CMP sensors: These are relatively inexpensive and easily replaced. Many auto parts stores can test them for you.
4. Test the ignition coil(s): A mechanic or experienced DIYer can test the coils for proper output.
5. Listen for the fuel pump: When you turn the key to the "on" position (before cranking), you should hear the fuel pump run briefly. If you don't, it could be a bad pump or a relay.
It's important to get a proper diagnosis as quickly as possible. Continuing to drive with these symptoms risks leaving you stranded. A qualified mechanic with experience in older vehicles will be able to systematically test the components listed above to pinpoint the cause.
