Got some misfire code, replaced the spark plugs, Jeep ran great for a few days. Then I made a good 200 mile trip, half way through code comes back, get home and it's running super shaky again. What would cause the plugs to go out so fast? I thought the engine could possibly be overheating since I had made such a long trip and it had happened before after I made the exact same trip. It normally runs fine when I'm just driving to work and other not super far. But what would be a good way to diagnose what exactly is failing in the cooling system rather than just randomly replacing stuff? Thanks