* Torque Converter: This is a high probability. A failing torque converter can cause a shudder or jerk when engaging, and if severely damaged, might prevent the engine from properly driving the transmission, leading to a stall. This is especially likely given the age of the car.
* Transmission Issues: Problems within the automatic transmission itself are another strong possibility. Worn clutches, low fluid, or internal valve body issues could all lead to this symptom. A slipping transmission can also contribute to the jerking. Check the transmission fluid level and condition – it should be pink and not burnt smelling.
* Shift Linkage/Cable: While less likely given the symptom description, a problem with the linkage or cable that connects the gear selector to the transmission could cause improper engagement. This could lead to a sudden jolt or stall if the transmission isn't engaging correctly.
* Computer/Sensor Issues: A less common but possible cause is a sensor malfunction or problem with the car's computer (PCM). A faulty crankshaft position sensor (CKP), camshaft position sensor (CMP), or throttle position sensor (TPS) could cause erratic engine behavior, potentially leading to stalling when the load of the transmission engages. A scan tool would be needed to diagnose this.
* Low Transmission Fluid: Critically low transmission fluid can cause similar symptoms due to lack of lubrication and hydraulic pressure.
Troubleshooting Steps:
1. Check Transmission Fluid: This is the first and easiest step. Check the fluid level and condition. If low, add the correct type (consult your owner's manual). If it's dark, burnt smelling, or otherwise contaminated, this indicates a serious problem within the transmission.
2. Listen for Unusual Noises: When the car is running in park or neutral, listen carefully for any unusual noises from the transmission area. Grinding, whining, or banging sounds suggest internal transmission problems.
3. Have the Car Scanned: A mechanic can use a scan tool to check for diagnostic trouble codes (DTCs) that might indicate a sensor or computer problem. This is crucial for ruling out electrical issues.
4. Check the Torque Converter: This is more involved and usually requires a professional. There are indirect ways to test its health but a direct diagnosis usually involves removing the transmission and inspecting the converter.
Given the age of the vehicle, a major transmission issue (like a failing torque converter) is a reasonable suspicion. It's important to get this checked out soon, as continuing to drive with a faulty transmission can cause further and more expensive damage. Taking it to a mechanic familiar with older vehicles is recommended for proper diagnosis.
