* Transmission Issues: This is the most probable cause. Several transmission problems could cause this:
* Low Transmission Fluid: Check your transmission fluid level. Low fluid can cause overheating and failure. If it's low, top it off (with the correct type of fluid for your transmission) and see if that solves the problem. However, low fluid is usually accompanied by other symptoms like slipping gears.
* Torque Converter Problems: The torque converter acts as a clutch between the engine and transmission. A failing torque converter can cause the engine to stall under load.
* Internal Transmission Problems: Worn clutch packs, a failing pump, or other internal problems can cause the transmission to fail when under stress. This is often more serious and requires professional repair.
* Shift Linkage/Cable Problems: Though less likely, a problem with the linkage or cable that controls shifting could be preventing the transmission from engaging properly.
* Engine Issues: While less likely given the timing (dies when shifting), engine problems can sometimes manifest in this way:
* Ignition System Problems: A weak coil, faulty distributor cap or rotor, or failing ignition wires could cause the engine to lose power under stress.
* Fuel Delivery Problems: A clogged fuel filter or a failing fuel pump might not be able to provide enough fuel under the increased load of driving.
* Neutral Safety Switch: This switch prevents the car from starting unless it's in park or neutral. A faulty switch might be sending incorrect signals, causing the engine to cut out when shifted into drive or reverse.
Troubleshooting Steps:
1. Check Transmission Fluid: This is the easiest and cheapest thing to check first. If it's low, add the correct fluid (consult your owner's manual).
2. Listen for Unusual Noises: When the engine dies, listen carefully for any unusual grinding, whining, or banging sounds from the transmission.
3. Check Engine Light: See if the check engine light is on. If so, get the codes read using an OBD-I scanner (appropriate for a 1991 model).
4. Inspect Wiring: Visually check the wiring related to the transmission, especially the neutral safety switch. Look for any obvious damage or corrosion.
Important Considerations:
* Professional Diagnosis: Transmission problems are often complex and require specialized knowledge and tools to diagnose and repair. It's best to have a mechanic inspect the car if the problem persists after checking the fluid. Attempting major transmission repairs yourself can be very difficult and potentially damaging.
* Safety: Driving a car with this problem is risky. The car could unexpectedly stall while driving, which is dangerous. Limit driving to short distances for testing only and have the car towed to a mechanic if necessary.
Don't try to drive the car extensively until you've determined the cause. The problem could worsen quickly and lead to more expensive repairs.
