My tick was an exhaust leak. Passenger side rear cylinder. Fixed under extended warranty. I thought it was a collapsed lifter. So I tried, Sea Foam, Royal Purple....... Finally crawled under the jeep and took pics of both manifolds. Sure enough, gasket had exhaust soot all around it. They found 2 broken bolts which needed extraction. Pulled cylinder head off which took 3 days. Now it drives like a brand new ride.