RepairPal Certified shops can diagnose and repair your 2006 Ford Explorer. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
I would first read all of this article, including the section on misfires. Then get your codes pulled and begin to trace. GUESSING will empty your check book with often no repair.
http://repairpal.com/check-engine-light