Here are some likely culprits based on your description:
* Fuel Pump: A weak or failing fuel pump can't supply enough fuel when the engine is idling or under load. When you stop, the engine might starve for fuel and die. The lack of power at higher speeds further supports this.
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to similar symptoms as a failing fuel pump. It's a relatively inexpensive and easy part to replace, so it's a good idea to check this even if the pump seems okay.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle's position. A faulty TPS can cause erratic idling, poor acceleration, and stalling.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor will lead to a lean or rich fuel mixture, causing poor performance and stalling.
* Ignition System: Problems with the ignition coil, distributor cap, rotor, spark plugs, or wires can cause misfires, poor acceleration, and stalling. This is less likely given the stalling upon idling, but it's still possible.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the position of the crankshaft, which is crucial for ignition timing. A faulty CKP can lead to stalling and poor performance.
* Computer/ECU: While less common, a faulty Engine Control Unit (ECU) or a problem with its wiring can cause a wide range of issues, including the ones you're experiencing.
* Vacuum Leaks: Leaks in the intake manifold or vacuum lines can cause erratic idling and poor performance.
What to do:
1. Read the Check Engine Codes: This is absolutely crucial. The codes will pinpoint the most likely problem areas.
2. Inspect the fuel system: Check the fuel filter (replace if necessary), listen for the fuel pump (should hum when the key is turned on), and check the fuel pressure (requires a fuel pressure gauge).
3. Check the obvious: Inspect the spark plugs, wires, distributor cap, and rotor for damage or wear.
4. Clean the MAF Sensor: Use MAF sensor cleaner (available at auto parts stores) to carefully clean the sensor.
5. Check for Vacuum Leaks: Visually inspect vacuum lines for cracks or damage.
Without knowing the specific check engine codes, any further diagnosis is speculation. Get those codes read first, and then you can focus your attention on the most likely culprits. If you're not comfortable working on your van yourself, take it to a mechanic.
