My 2000 ES is sending misfires on all 6 cylinders. Replaced all plugs and coils. Ran great 100 miles then wham, garbage. I'm have a valve cover gasket leak, get oil on #4. Plan on replacing ASAP. It runs better cold. I noticed it started running rough soon after putting in different type of oil ( synthetic) 5w30. Should the gasket repair be enough? I feel that a oil change would be a good solution. 195k miles. Are there any advise about engine flush or agents to remove build up? No metal in oil. Thanks.
