Here's why:
* Check Engine Light: This indicates a fault detected by the onboard computer. You'll need to get the diagnostic trouble codes (DTCs) read using an OBD-II scanner. This is the *first* step. The codes will pinpoint the likely culprit.
* High RPMs at Idle after driving: The IAC valve controls the idle speed. If it's malfunctioning (stuck open, dirty, or failing), it might allow too much air into the engine at idle, causing the high RPMs. When the engine is warm, this problem is more likely to manifest.
* No Movement: The high idle likely overwhelms the torque converter's ability to lock up, preventing the van from moving forward.
Other possibilities (less likely but still possible, especially if the DTCs don't point to the IAC):
* Transmission issues: While less likely given the specific symptoms, a problem in the transmission could cause the engine to rev without moving. This is more likely to be accompanied by other transmission symptoms like slipping or hard shifting.
* Throttle Position Sensor (TPS): A faulty TPS can provide incorrect information to the engine computer, leading to incorrect idle control.
* Mass Airflow Sensor (MAF): While less common for this specific symptom, a bad MAF sensor can affect the air-fuel mixture and idle.
What you should do:
1. Get the Diagnostic Trouble Codes (DTCs): This is crucial. Auto parts stores often offer free code reading services. Write down the codes.
2. Clean the IAC valve: This is a relatively easy DIY repair. Look up a YouTube video specifically for a 1998 Ford Windstar IAC valve cleaning. This is a cheap and potentially effective first step.
3. Inspect the Throttle Body: While you're cleaning the IAC valve, inspect the throttle body for buildup. Cleaning it can also help.
4. If cleaning doesn't solve the problem: Based on the DTCs, you may need to replace the IAC valve, TPS, or MAF sensor. A mechanic might be necessary for diagnosis and/or replacement if you are not comfortable with auto repair.
Don't ignore the check engine light. Continuing to drive with a potential problem could lead to further damage. The inexpensive diagnostic step (reading the codes) will give you much more direction.
