Most Common Causes:
* Spark Plug/Ignition Coil: This is the most likely culprit. A faulty spark plug or ignition coil for cylinder 4 won't produce the spark needed for combustion.
* Check: Visually inspect the spark plug for damage (cracks, fouling, excessive wear). Test the spark plug with a spark tester. If possible, swap the suspected bad coil with one from another cylinder (carefully noting which cylinder it came from) to see if the misfire moves.
* Worn or Damaged Spark Plug Wires: A cracked, frayed, or loose spark plug wire can prevent a proper spark from reaching the plug.
* Check: Inspect the wire visually for damage. Look for arcing or visible wear.
* Injector Problems: A clogged or faulty injector for cylinder 4 won't deliver the necessary fuel.
* Check: This is more difficult to diagnose at home. A fuel pressure test and/or injector flow test is usually needed. You may need a professional mechanic for this.
* Compression Issues: Low compression in cylinder 4 means the cylinder isn't properly compressing the air/fuel mixture, leading to a weak or absent ignition. This could indicate problems with valves, piston rings, or a head gasket.
* Check: Requires a compression test using a compression gauge. This should be done by a mechanic unless you have experience.
* Vacuum Leaks: A significant vacuum leak can affect the engine's air/fuel mixture, impacting combustion in various cylinders, including #4.
* Check: Requires a visual inspection of all vacuum hoses and connections for cracks or disconnections. A smoke test is often used by mechanics to locate vacuum leaks.
* Engine Control Module (ECM) Issues: While less common, a problem with the ECM could cause a misfire in a single cylinder. This is difficult to diagnose without specialized equipment.
Troubleshooting Steps:
1. Check Engine Light (CEL): Obtain the diagnostic trouble codes (DTCs) using an OBD-II scanner. This will give you a starting point. The code(s) related to cylinder 4 misfire will be crucial.
2. Visual Inspection: Inspect the spark plug, wire, and ignition coil for cylinder 4. Look for obvious damage or signs of wear.
3. Spark Test: Test the spark plug and ignition coil for proper spark using a spark tester.
4. Swap Components (If Possible): Swap the spark plug, ignition coil, and even the spark plug wire with a known good one from another cylinder (making sure to note where things go). This helps isolate the faulty component.
5. Advanced Diagnostics: If the problem persists, you'll likely need more advanced diagnostics, such as a compression test, fuel pressure test, injector flow test, or a vacuum leak test, likely performed by a mechanic.
Important Considerations:
* Safety First: Work on a vehicle involves risks. Disconnect the negative battery terminal before starting any work. Be aware of hot components and moving parts.
* Professional Help: If you're not comfortable performing these checks yourself, take your Ranger to a qualified mechanic for diagnosis and repair. Improperly diagnosing and fixing a misfire could lead to further damage.
Ignoring a misfire can cause serious damage to your engine over time. Addressing it promptly is essential.
