High-Probability Causes:
* Transmission Issues: This is often the primary suspect. Possible problems include:
* Low Transmission Fluid: Check the fluid level immediately. Low fluid can cause severe damage and stalling. The fluid should be checked with the engine running and warmed up, and you should also inspect the fluid for color and smell (burnt fluid is a bad sign).
* Failing Torque Converter: The torque converter transmits power from the engine to the transmission. A failing converter might not be able to handle the load when shifting into drive. This often presents as a shudder or slipping before stalling.
* Internal Transmission Problems: Worn clutches, bands, or other internal components can lead to a failure to engage properly under load. This often requires a professional transmission inspection and repair.
* Shift Linkage/Cable Issues: A problem with the linkage or cable could be preventing the transmission from shifting correctly into drive.
* Engine Issues: While less likely than transmission problems, engine issues can also cause stalling when shifting into drive:
* Insufficient Engine Power: A weak engine, due to worn components, poor fuel delivery (clogged fuel filter, bad fuel pump), or ignition problems (spark plugs, wires, distributor), might not be able to overcome the increased load when the transmission engages.
* Vacuum Leaks: Vacuum leaks can disrupt the engine's operation, leading to stalling under load.
Less-Likely but Still Possible Causes:
* Computer Issues: Although less common in older vehicles, a faulty computer (PCM) or related sensors could contribute to the problem by misinterpreting engine parameters and causing improper fuel delivery or ignition timing.
* Wiring Problems: Damaged or corroded wiring related to the transmission or engine control systems could disrupt the power flow, leading to stalling.
Troubleshooting Steps:
1. Check Transmission Fluid: This is the *absolute first* step. Low or burnt fluid is a major red flag.
2. Listen for Unusual Noises: When trying to put the van into drive, listen carefully for any grinding, whining, or other abnormal sounds from the transmission.
3. Check Engine and Transmission Mounts: Worn mounts can cause excessive vibration, potentially affecting transmission engagement.
4. Inspect Vacuum Lines: Look for cracks or disconnections in vacuum lines related to the engine and transmission.
5. Obtain a Diagnostic Scan: A professional mechanic can use a scan tool to check for any trouble codes stored in the computer system. This can pinpoint potential electrical or sensor issues.
Important Note: Attempting to drive the vehicle while it's exhibiting this problem could cause further damage, particularly to the transmission. It's best to have it towed to a mechanic for diagnosis and repair. Ignoring the problem could result in costly repairs.
