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1997 Ford F-150 P0302 Misfire Diagnosis: Plug Wire, Coil Pack or Injector?

Model: 97 F-150 Fault Code: P0302 Posted: 2010-01-12 19:30

I recently encountered a persistent misfire issue on my 1997 Ford F-150 4.2L V6 with 110,000 miles. The vehicle has pulled Diagnostic Trouble Code P0302 (Cylinder 2 Misfire). After checking the obvious components, I found that the spark plug boot was not fully seated—its metal end wasn't properly snapped onto the plug. I reinstalled it correctly and the engine ran smoothly for about 2 miles before the check engine light returned and symptoms resumed. I compared spark plugs between cylinders 1 and 2; they appear identical in condition. The ignition coil pack has never been replaced, and the plug wires show resistance readings of approximately 4 to 6 ohms. Both plugs and wires were originally installed in 2005 and are now around 17.5 years old. I'm considering replacing the spark plugs and wires again, but I'd prefer a more targeted diagnosis before spending additional money. Could the issue be related to the coil pack? While fuel and air delivery systems have not been fully addressed, these three components—spark plug, ignition wire, or coil pack—are commonly linked to P0302 misfires. Any insights or troubleshooting steps would be greatly appreciated.

Related fault codes

P0302

Comments (5)

Anonymous 2010-01-13 06:46

Does the misfire occur consistently under load? For example, when climbing hills or accelerating?

Anonymous 2010-01-13 18:55

The engine misfires and stumbles specifically during heavy loads—such as when driving uphill or passing another vehicle.

Anonymous 2010-01-13 20:23

Lower-quality ignition wires may not last four years. If the boot wasn't fully seated initially, it could have caused a carbon track on the spark plug. A simple test is to swap cylinder 2's spark plug with cylinder 1 and see if the misfire follows. If the code stays in cylinder 2 after swapping, then the issue may be with the ignition wire. Next, try replacing the wire with a known good one. If the problem persists, perform a compression test or cylinder leakage test on cylinder 2. Also check for vacuum leaks. You could attempt an injector swap or conduct a static resistance test on the fuel injector—elevated ohms compared to other cylinders may indicate a faulty injector as the root cause.

Anonymous 2010-01-14 19:49

Thanks, Jeff! I'll perform the wire and plug swaps soon. The cheap wires are likely the culprit based on the age and history of the setup.

Anonymous 2010-01-15 19:39

The issue was resolved—confirmed by swapping components. Replacing the spark plug wires fixed the P0302 misfire. The truck now runs smoothly with improved idle and full power. Thanks for all the helpful suggestions!