* Idle Air Control (IAC) Valve: This valve controls the amount of air entering the engine when it's idling. If it's dirty, malfunctioning, or stuck closed, the engine won't get enough air to stay running at idle. Holding the gas pedal down increases the airflow, bypassing the IAC's faulty regulation.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of the throttle plate. A faulty TPS can send incorrect information, leading to improper fuel delivery at idle. The engine might need the extra fuel from depressing the gas pedal to compensate for the inaccurate signal.
* Mass Airflow Sensor (MAF) Sensor: Less likely, but a dirty or faulty MAF sensor could also contribute. This sensor measures the amount of air entering the engine. An inaccurate reading could cause the engine to miscalculate the fuel/air mixture.
* Fuel System Issues (Less Likely): While less probable given the symptom, low fuel pressure or a problem with the fuel pump could theoretically cause this. However, these usually result in more significant starting problems.
* Vacuum Leaks: A significant vacuum leak could disrupt the idle mixture, making it difficult to maintain idle speed.
Troubleshooting Steps:
1. Check the IAC Valve: Locate the IAC valve (usually on the throttle body). Try cleaning it with electronic parts cleaner. If it's visibly dirty or damaged, replacement might be necessary.
2. Inspect the Throttle Body: While you're there, clean the throttle body itself. Accumulated grime can interfere with the smooth operation of the throttle plate and sensors.
3. Check the TPS: You'll likely need a multimeter to test the TPS voltage output against the manufacturer's specifications (found in a repair manual). A faulty TPS often needs replacement.
4. Check for Vacuum Leaks: Visually inspect all vacuum hoses for cracks or disconnections. A spray bottle with soapy water can help detect leaks by creating bubbles where air is escaping.
5. Check the MAF Sensor: Clean the MAF sensor carefully with MAF sensor cleaner (avoid touching the sensor element). Replacement might be needed if cleaning doesn't resolve the issue.
6. Professional Diagnosis: If you're not comfortable performing these checks or if the problem persists, take your Windstar to a qualified mechanic. They have diagnostic tools that can pinpoint the exact cause more efficiently.
Important Note: Always disconnect the negative battery terminal before working on any electrical components in your vehicle. Consult a repair manual specific to your 1996 Ford Windstar for detailed diagrams and procedures.
