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P0302 Diagnostic and Fix for 1998 Mercury Mystique - DIY Guide

Model: 98 Mercury Mystique Fault Code: P0302 Posted: 2008-01-09 17:55

Hello everyone, My wife's 1998 Mercury Mystique (4-cylinder, automatic, 105,000 miles) has a check engine light and a P0302 diagnostic code indicating a misfire in cylinder #2. What should be my first step to troubleshoot this issue myself before visiting the service department? Are there any common causes I can address or replace on my own? I'm looking for practical, cost-effective solutions that don't require professional diagnosis. Any advice on how to narrow down the problem would be greatly appreciated. Thanks, Fred

Related fault codes

P0302

Comments (3)

Anonymous 2008-01-10 07:54

Did you perform a recent tune-up? Check the official forum article on P0302 codes for detailed troubleshooting steps. This code often points to worn spark plugs or faulty ignition wires. A simple inspection and replacement may resolve the issue. Good luck — please update us if you find a solution.

Anonymous 2008-01-13 09:55

The P0302 code has disappeared after two days. I replaced the spark plugs and ignition wires as suggested in the forum. Upon inspection, cylinder #2 had severely worn plugs with gaps up to 0.125 inches — far beyond the standard 0.050-inch gap. The #4 plug was particularly difficult to remove and required soaking in WD-40 for about 20 minutes before extraction. After installing a new set of Autolite spark plugs and Belden 8mm ignition wires, the car is running smoothly again. This confirms that worn spark components were the root cause. Thanks for the helpful guidance! Fred

Anonymous 2008-01-13 11:28

Great to hear it's resolved! A common fix for P0302 in older Mercury Mystique models is replacing old or degraded spark plugs and wires — especially in high-mileage vehicles. This DIY approach saves money and often resolves the issue effectively.