Random misfire

[libertybob]

2003 3.7 had random misfire on cylinder 3 and 6 for last 20,000 miles. I checked all kinds of things but no joy. Engine ran fine except occasionally misfire on startup. Finding no root cause, I erased the check engine light and would run up to 600 miles before misfire repeated. Finally, I read the maintenance schedule in the owners manual. I had replaced the spark plugs when I got the Jeep with OEM plugs. The maintenance schedule calls for replacing the plugs at 30k miles. I had put 60k on those plugs. I replaced them with new OEM plugs and guess what! No more misfire! When all else fails, read the owners manual. As my wife says, check the simple things first. If you are chasing a misfire, when did you last replace the plugs?

 

[apropes]

Your Jeep is especially finicky when it comes to the brand and type of plugs. You were wise to go with OEM. Great lesson on how important it is to know what maintenance is called for by the manufacturer and (ideally) follow it.

 

[Ksat]

Sorry, wrong thread.