Engine-Related Issues:
* Insufficient fuel: Check your fuel level. A low fuel level can cause erratic running, especially under load (like when shifting into gear). Also check the fuel filter; a clogged filter restricts fuel flow.
* Faulty fuel pump: A weak or failing fuel pump can't deliver enough fuel at the required pressure, leading to rough running and stalling under load.
* Clogged air filter: A restricted airflow can starve the engine of oxygen, causing similar symptoms.
* Spark plugs/wires/distributor cap & rotor (if applicable): Worn or faulty ignition components can lead to misfires, resulting in rough running and stalling. This is especially likely in a vehicle of this age.
* Mass Airflow Sensor (MAF) or Throttle Position Sensor (TPS): These sensors regulate fuel/air mixture. A faulty sensor provides inaccurate readings, leading to poor engine performance and stalling.
* Crankshaft Position Sensor (CKP): This sensor tells the engine's computer where the crankshaft is in its cycle. A faulty CKP sensor can prevent the engine from starting or running consistently.
* Low engine compression: Worn piston rings or valve problems can cause low compression, making it difficult for the engine to generate enough power to move the vehicle.
Transmission-Related Issues:
* Low transmission fluid: Check the transmission fluid level and condition. Low fluid or severely contaminated fluid can cause problems shifting and stalling.
* Torque Converter Problems: A faulty torque converter might not be able to efficiently transfer power from the engine to the transmission, leading to stalling when engaging the drive.
* Transmission Problems (More Serious): Internal transmission problems are a possibility, though less likely to cause a *sudden* stall upon shifting. However, a failing transmission might exhibit rough running *before* stalling under load.
Other Possibilities:
* Alternator: A failing alternator might not be able to provide enough power to the engine, leading to stalling. Check your battery voltage.
* Wiring Issues: A short circuit or corroded connection in the electrical system can cause intermittent problems.
Troubleshooting Steps:
1. Check the obvious: Fuel level, air filter, and transmission fluid level.
2. Listen to the engine: Does it make unusual noises (knocking, ticking, etc.)? This can give clues to the problem.
3. Check the battery voltage: A weak battery can cause starting and running issues.
4. Have the codes read: Use an OBD-II scanner to check for diagnostic trouble codes (DTCs). This is often the quickest way to pinpoint the problem.
It's crucial to have a mechanic diagnose the problem. The symptoms you describe could be caused by several different issues, and improperly diagnosing and fixing the problem can lead to further damage. The cost of a proper diagnosis is far less than the cost of potentially damaging further parts by guessing.
