* Ignition System: This is a prime suspect. Intermittent problems could stem from:
* Distributor Cap and Rotor: Cracks or corrosion can cause poor spark delivery, leading to stalling. These are relatively inexpensive parts to replace.
* Ignition Coil: A failing coil can produce weak or inconsistent spark, especially under load.
* Ignition Wires: Worn or damaged wires can lead to misfires and stalling.
* Pick-up Coil (in the distributor): This component senses the position of the rotor and sends a signal to the ignition coil. A failing pick-up coil can cause intermittent misfires.
* Fuel System: Problems here can also cause intermittent stalling:
* Fuel Pump: A weak fuel pump might struggle to deliver enough fuel under load, leading to stalling. It might recover when the engine is off, then restarts when pressure builds up again.
* Fuel Filter: A clogged fuel filter restricts fuel flow.
* Loose or Corroded Fuel Connections: Poor connections can interrupt fuel supply.
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the engine's rotational position. A faulty CKP sensor can cause the engine to stall, but since it's an intermittent problem, it's likely just starting to fail.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle's position. A malfunctioning TPS can lead to erratic fuel delivery and stalling.
* Alternator: Although less likely to cause an immediate stall, a failing alternator might not be charging the battery properly. If the battery is low, the engine might stall, but then restart after a short rest to allow the battery to recover (slightly).
Troubleshooting Steps:
1. Check the obvious: Look for loose or corroded battery terminals. Clean them if necessary.
2. Inspect the distributor cap and rotor: Look for cracks, burns, or corrosion.
3. Check the ignition wires: Look for damage or fraying.
4. Listen for unusual noises: While the engine is running, listen for unusual clicking, ticking, or whirring sounds from the ignition system or fuel pump.
5. Check the fuel filter: If it's visibly dirty or clogged, replace it.
6. Have the battery and charging system tested: Make sure the alternator is charging properly.
7. Consult a repair manual specific to your 1988 G20 van: This will provide diagrams and troubleshooting guides.
Because the problem is intermittent, diagnosing it will likely require some detective work. You may need to drive the van until it stalls to try and narrow down the cause while it's actively exhibiting the problem. If you're not comfortable working on the vehicle yourself, take it to a mechanic who specializes in older vehicles. They will have the experience and tools to properly diagnose this issue.
