1. Diagnose the Problem:
Before you start cleaning, you *must* determine the cause of the high idle. A simple check engine light (CEL) scan is crucial. Auto parts stores often offer this service for free. The diagnostic trouble codes (DTCs) will pinpoint potential issues, saving you time and effort. Common causes of high idle include:
* Vacuum Leaks: Cracks or holes in vacuum lines can cause erratic idle. Inspect all vacuum lines visually.
* Idle Air Control (IAC) Valve: This valve regulates air flow at idle. A dirty or malfunctioning IAC valve is a frequent culprit. Cleaning it might help, but replacement may be necessary.
* Throttle Position Sensor (TPS): A faulty TPS can send incorrect signals to the engine computer, leading to high idle.
* Mass Air Flow (MAF) Sensor: A dirty MAF sensor can also cause incorrect readings, affecting the air/fuel mixture and idle speed.
* Engine Coolant Temperature (ECT) Sensor: An inaccurate ECT sensor can cause the engine to idle high, especially when cold.
* PCV Valve: A clogged PCV valve can cause excessive crankcase pressure, leading to various issues, including high idle.
2. Cleaning the Throttle Body:
If the CEL scan doesn't reveal a specific problem, cleaning the throttle body is a reasonable next step. Here's how:
* Disconnect the Battery: This is crucial to prevent accidental shorts.
* Locate the Throttle Body: It's usually located on the intake manifold, where the air intake connects to the engine.
* Disconnect Components: Disconnect the throttle cable, the IAC valve (if it's separate), and the electrical connectors to the TPS.
* Clean Thoroughly: Use a throttle body cleaner (available at auto parts stores). Spray it into the throttle body, carefully avoiding spraying into the MAF sensor if it's nearby. Use a clean rag or shop towel to wipe away debris.
* Inspect for Damage: Look for any cracks, damage, or debris inside the throttle body.
* Reassemble: Carefully reconnect everything in the reverse order of removal.
3. Gaskets:
You might *not* need a gasket. Many throttle bodies use a simple seal that doesn't require replacement during cleaning. However, if the old gasket is damaged or you're unsure, it's best to replace it with a new one. It's a relatively inexpensive part. Check an auto parts store for a gasket specific to your 1997 Ford E150 5.4L.
4. After Cleaning:
Reconnect the battery and start the engine. Check the idle speed. If the high idle persists, it's likely a more serious issue than a dirty throttle body.
5. Next Steps if the Problem Remains:
* IAC Valve Cleaning or Replacement: Clean the IAC valve using throttle body cleaner or consider replacing it.
* TPS Inspection/Replacement: Have the TPS checked or replaced.
* MAF Sensor Cleaning/Replacement: Clean the MAF sensor carefully (use a MAF sensor cleaner) or replace it.
* Vacuum Leak Check: Carefully inspect all vacuum lines for cracks or loose connections. Use a vacuum gauge for a thorough check.
* Professional Diagnosis: If you've tried the above steps and the problem persists, take your vehicle to a qualified mechanic for a professional diagnosis.
Important Note: Working on your vehicle's engine can be dangerous. If you're not comfortable working on your vehicle, consult a professional mechanic. Improper repair attempts can lead to further damage and injury.
