1. Fuel Delivery Problems:
* Fuel Pump: A weak fuel pump might provide sufficient fuel for idling but struggle to supply the increased demand under load. Hard starting also supports this. Check fuel pressure.
* Fuel Filter: A clogged fuel filter will restrict fuel flow, leading to similar symptoms. Replace it as preventative maintenance even if it seems fine.
* Fuel Injectors: Clogged or malfunctioning injectors can prevent proper fuel atomization and delivery. A fuel injector cleaning or replacement might be necessary.
* EGR Valve: A stuck-open EGR valve can lean out the fuel mixture under load, causing bogging. Check for proper operation.
2. Ignition System Issues:
* Ignition Coil(s): A failing ignition coil might not provide sufficient spark under load. This can cause misfires and a rough running engine, leading to bogging.
* Spark Plugs & Wires: Worn or damaged spark plugs and wires can lead to misfires, especially under load. Replace them as a preventative measure.
* Distributor Cap & Rotor (if applicable): If your 4.3L has a distributor, inspect the cap and rotor for cracks or wear. These can interrupt spark delivery.
3. Air Intake System:
* Mass Airflow Sensor (MAF): A faulty MAF sensor will provide incorrect air/fuel mixture information to the computer, leading to poor performance. Cleaning or replacement might be needed.
* Air Filter: A dirty air filter restricts airflow, leading to a lean fuel mixture and poor performance. Replace it regularly.
* Vacuum Leaks: Leaks in the vacuum system can cause incorrect engine operation. Check all vacuum lines and connections for cracks or disconnections.
4. Transmission Issues (Possibly Related):
The fact that the van won't go even after the engine is running suggests a transmission problem *might* be related or even the primary culprit. This could be separate from the engine problems, or the engine problems could be *causing* transmission issues (due to lack of power). Consider:
* Transmission Fluid Level & Condition: Low or dirty transmission fluid can severely impact shifting and performance.
* Torque Converter: A faulty torque converter can prevent power transfer from the engine to the transmission.
Troubleshooting Steps:
1. Check the obvious: Start with the simplest things. Change the air filter, check your transmission fluid level (and its condition – it should be pink/reddish and not dark brown or burnt-smelling). Check all fluid levels.
2. Fuel Pressure Test: This is crucial to determine if the fuel pump is working properly. A mechanic can easily perform this test.
3. Code Scan: Get the OBDII trouble codes read by a scanner (auto parts stores often offer this service for free). This can pinpoint potential electronic issues.
4. Visual Inspection: Examine all hoses, wires, and connections for obvious damage or leaks.
5. Professional Diagnosis: If you're not comfortable performing these checks, take your Astro to a trusted mechanic. They have specialized tools and expertise to diagnose the issue more efficiently.
Because of the combination of hard starting and inability to move, don't overlook the transmission. It's possible a failing component in the transmission or a severe lack of power from the engine is preventing it from engaging properly. A proper diagnosis is needed to determine the root cause, especially since several systems could be contributing to the problem.
