The low idle and stalling indicate a problem, likely one of these:
* Dirty or Failing IAC Valve: The IAC valve controls the air bypass at idle. Dirt or carbon buildup prevents it from opening correctly, leading to low idle. Cleaning it (with throttle body cleaner) is often a first step, and replacement might be necessary.
* Faulty TPS: The TPS tells the computer the throttle position. A faulty TPS can give incorrect readings, leading to erratic idle and stalling. It's relatively inexpensive to replace.
* Vacuum Leaks: Check all vacuum hoses for cracks or leaks. Even a small leak can significantly affect idle. Pay close attention to the hoses connected to the intake manifold and the brake booster.
* Dirty Throttle Body: A dirty throttle body can restrict airflow and cause idle problems. Cleaning it with throttle body cleaner is recommended.
* MAF Sensor (Mass Airflow Sensor): While less likely to directly cause a low idle, a faulty MAF sensor can lead to incorrect fuel mixture which might manifest as low or erratic idle.
* PCV Valve (Positive Crankcase Ventilation): A clogged PCV valve can cause a vacuum leak or build pressure in the crankcase, affecting the engine's operation.
* Fuel Pressure Issues: Low fuel pressure can also lead to poor idle and stalling. This requires a fuel pressure gauge to diagnose.
How to Proceed:
1. Visual Inspection: Begin with a thorough visual inspection of the engine bay, focusing on vacuum hoses, the throttle body, and the IAC valve. Look for obvious cracks, loose connections, or excessive dirt.
2. Clean the Throttle Body and IAC Valve: Use a throttle body cleaner and carefully clean both the throttle body and the IAC valve. Make sure the throttle plate moves freely. This is the easiest and cheapest first step. Follow the cleaner's instructions carefully.
3. Check Vacuum Hoses: Inspect all vacuum hoses for cracks, leaks, or loose connections. Replace any damaged hoses.
4. Check for Diagnostic Trouble Codes (DTCs): Your van likely has a diagnostic port (OBD-I, possibly). You'll need a code reader to retrieve any stored trouble codes. These codes can pinpoint the problem. Auto parts stores often offer free code reading services.
5. Advanced Diagnosis: If cleaning and visual inspection don't solve the problem, you'll need to test the TPS, IAC valve, and potentially the MAF sensor. This usually requires a multimeter and some knowledge of automotive electronics. If you're not comfortable with this, take it to a mechanic.
Important Note: Do NOT attempt to adjust any screws on the throttle body or IAC valve unless you're absolutely certain of what you're doing. These systems are electronically controlled, and incorrect adjustment can cause more serious problems. The focus should be on diagnosing and repairing the underlying cause of the low idle, not just raising the idle speed temporarily.
