Sum have found the iridium plug to be sensitive/fragile. They went out on my wives on the interstate and began bucking intermittently gradually increasing in frequency on long hills. New fixed it. Immediately. I suspect some get dropped in production and installed. The problem crops up at some later time. No real set time limit just before 75,000 miles.
Last edited by papa tiger; 10-28-2013 at 07:05 PM.