Most Likely Culprits:
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the engine's rotational position. A faulty CKP sensor can cause erratic running, bucking, and stalling, especially when the engine is under load (acceleration) or idling. This is a very common cause of these symptoms in older vehicles.
* Mass Airflow Sensor (MAF Sensor): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor provides inaccurate readings, leading to a poor air/fuel mixture, resulting in bucking and stalling.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle's position. A faulty TPS can cause similar issues to a bad MAF sensor. Incorrect throttle position readings lead to incorrect fuel delivery.
* Fuel Pump or Fuel Filter: A weak fuel pump or a clogged fuel filter can restrict fuel flow, leading to hesitation, bucking, and stalling, especially when the engine is demanding more fuel (acceleration).
* Ignition System: Worn spark plug wires, faulty spark plugs, or a failing ignition coil can cause misfires, leading to bucking. A total ignition system failure could result in a stall.
Less Likely, but Possible:
* Computer (PCM) Issues: Though less common, a failing engine control module (PCM) can cause intermittent problems like these. This is usually a more expensive and involved fix.
* Vacuum Leaks: A significant vacuum leak can disrupt the engine's operation, leading to rough running and stalling.
Troubleshooting Steps:
1. Check Engine Light: Does the Check Engine Light illuminate? If so, get the diagnostic trouble codes (DTCs) read using an OBD-II scanner. This will give you a starting point. Auto parts stores often offer this service for free.
2. Inspect the obvious: Visually inspect all vacuum lines for cracks or disconnections. Look at the spark plug wires for damage or wear.
3. Start with the easy/cheap fixes:
* Clean the MAF sensor: Use a MAF sensor cleaner (available at auto parts stores) to carefully clean the sensor element. Don't touch the sensor element with your fingers.
* Replace the fuel filter: This is a relatively inexpensive and simple replacement that often solves fuel delivery problems.
4. Professional Diagnosis: If the above steps don't resolve the issue, take your Lumina to a trusted mechanic for a professional diagnosis. They can use diagnostic tools to pinpoint the problem more accurately.
Remember to always be safe when working on your car. If you're not comfortable working on your car yourself, it's best to seek professional help. A misdiagnosis can lead to unnecessary expense or even damage to your engine.
