What is your question?
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What is your question?
Check engine light keeps coming on and codes keep saying p 307 and 302 keep faulting
What makes this problem better or worse?
Gets worse the more it runs
How long has your 1998 Mercury Grand Marquis had this problem?
1 week
1 Reply
Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. Those seem to be misfire codes (P0307 and P0302 -- cylinder 7 and cylinder 2 misfire recorded). The most likely cause -- but not only possible cause - are coils that are failing or that have boots that are leaking coil spark, causing misfire. I would suggest replacing #2 and #7 coil and replace all 6 other coil boots. Use ONLY Ford Motorcraft parts for this -- hopefully still available. The boots can be purchased separate. Since 2 and 7 show active misfires, I would replace those coils fully. You should also replace the spark plugs with proper quality and correctly gapped ones. Like I said, there are more possible causes but this is by far the most common. Beyond that, have hands on testing performed to find out what's going on. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.