This could be caused by several issues, including:
* Spark plug problems: A faulty spark plug (cracked insulator, worn electrode, etc.) in cylinder 4 is a common culprit.
* Ignition coil problems: The ignition coil responsible for firing cylinder 4 might be malfunctioning. Windstars often have individual coils for each cylinder, making this a likely suspect.
* Worn or damaged wires: A damaged or loose spark plug wire leading to cylinder 4 can prevent a proper spark.
* Injector problems: A clogged or malfunctioning fuel injector in cylinder 4 could prevent fuel from reaching the cylinder.
* Low compression: Low compression in cylinder 4 means the cylinder isn't able to generate enough pressure to combust the fuel-air mixture effectively. This could be due to worn piston rings, a valve problem, or a head gasket leak.
* Vacuum leak: A significant vacuum leak can affect the air-fuel mixture, leading to misfires.
Troubleshooting steps:
Since several components could be causing this, you'll need to systematically check them. It's usually best to start with the easiest and cheapest options first:
1. Inspect the spark plug and wire: Remove the spark plug from cylinder 4, visually inspect it for damage, and check the wire for cracks or fraying. Replace the plug and wire if necessary.
2. Check the ignition coil: Visually inspect the coil for cylinder 4 for any obvious damage. You may need a multimeter to test its resistance, although this often requires some automotive electrical knowledge.
3. Check for vacuum leaks: Visually inspect all vacuum hoses and connections for cracks or leaks.
4. Check the fuel injector: This is more involved and may require a fuel pressure test or injector diagnostic tool.
If you're not comfortable performing these checks yourself, it's best to take your Windstar to a qualified mechanic for diagnosis and repair. Attempting repairs without proper knowledge can potentially cause further damage.
