I ran auto-rx in my ford explorer with 4.0l sohc engine for about 2,000 miles. Truck has 138,000 miles. Truck has just started the rinse cyle. During this time the truck developed a rattle only at warm idle. Rattle does not appear when cold or when reved above idle. Vehicle seem to run fine. Could the auto-rx have dislodged enough gunk to temorarly block passages while cleaning?