Everything in my 100s is current on maintenance (recently replaced timing belt for 2nd time at 199k). Engine light came on flashing when accelerating and stops at slow speeds or idle. You can hear a "tick tick tick" from manifold. Is this a misfire? Sparkplug or coil issue? I am in Houston, Texas. We had an unusual winter storm here yesterday and today, but i doubt this is weather related. Any recommendations?