Last July our 2005 Ford Lariat F150 with a 5.4 Triton engine which had 87,000 miles started to run rough. We took the vehicle to the dealership & their tests found #3 misfiring & #4 in mode 6. They completed a whole tune up and replaced #3 coil. While taking out the #3 plug, it broke and they had to restract the plug to complete the tune-up. They also performed a fuel induction service. Additionally, I had the transmission serviced. Since the tune-up, the truck idles rough & vibrates the truck. We have taken the truck back to the dealership, they hooked it up to the computer but it did not find a problem.
Any suggestions on what might be the problem.