1. Idle Air Control (IAC) Valve: This valve regulates air flow at idle. A dirty or faulty IAC can cause erratic idling, high RPM during warm-up, and stalling.
* Troubleshooting: Try cleaning the IAC valve with carburetor cleaner (following instructions carefully). If cleaning doesn't resolve the issue, replacement might be necessary.
2. Throttle Position Sensor (TPS): The TPS tells the computer the throttle's position. A faulty TPS can lead to incorrect fuel delivery and idle problems.
* Troubleshooting: Often, a faulty TPS will throw a diagnostic trouble code (DTC). Use a code reader to check for any codes. A multimeter can be used to test the TPS voltage output (refer to a repair manual for specific voltage readings).
3. Mass Airflow Sensor (MAF) Sensor: The MAF measures the amount of air entering the engine. A dirty or faulty MAF sensor will cause the computer to deliver incorrect amounts of fuel.
* Troubleshooting: Carefully clean the MAF sensor with MAF sensor cleaner (avoid touching the sensor element). Replacement is often necessary if cleaning doesn't work.
4. Fuel System Problems:
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to rough running and stalling. Replace the fuel filter.
* Fuel Pump: A weak or failing fuel pump may not deliver enough fuel, especially when idling. Listen for the fuel pump's whine when the key is turned on. Low fuel pressure testing might be required.
* Fuel Injectors: Clogged or faulty injectors can cause misfires and poor idling. Injectors might need cleaning or replacement.
5. Ignition System Problems:
* Spark Plugs and Wires: Worn or fouled spark plugs and cracked or damaged spark plug wires can cause misfires, leading to rough idling and stalling. Inspect and replace as needed.
* Distributor Cap and Rotor (if applicable): These components can wear out, causing poor ignition. Inspect for cracks, corrosion, or wear. Replace if necessary.
* Ignition Coil: A weak or faulty ignition coil can also cause misfires.
6. Vacuum Leaks: Leaks in the vacuum system can disrupt engine operation, affecting idle and causing stalling. Inspect all vacuum hoses for cracks or disconnections.
7. Computer/PCM Issues (Powertrain Control Module): Though less common, a failing PCM can cause a wide range of issues, including those you describe. This is usually diagnosed last after other possibilities have been eliminated.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use a code reader to scan for any stored codes. This will often point you in the right direction.
2. Visual Inspection: Check for obvious problems like loose vacuum hoses, damaged wiring, or anything out of the ordinary.
3. Start with the simplest and cheapest solutions first: Clean the IAC valve and MAF sensor, replace the fuel filter, and inspect the spark plugs and wires.
4. Consult a Repair Manual: A repair manual specific to your 1993 Ford Explorer will provide detailed diagnostic procedures and specifications.
If you're not comfortable working on your vehicle yourself, take it to a qualified mechanic for diagnosis and repair. The issue could be a combination of problems, so a professional diagnosis is often the most efficient approach.
