I had this happen @35K miles. the spark plug wire was rubbing on the exhaust manifold heat shield. The insulation rubbed off, and the spark was arching to the heat shield instead and not going to the spark plug.
A forum community dedicated to Jeep Wrangler JK owners and enthusiasts. Come join the discussion about performance, modifications, classifieds, reviews, engine swaps, troubleshooting, suspension, and more!