Started having hard start 6 weeks ago, took to dealership and found no codes and nothing wrong. Truck started sputtering and check engine light came on, took it Dealership . "P0304 and P0300 Codes present in ECM misfire on #4. Replaced all 6 (original) spark plugs and cleaned throttle body drove 10 miles-no code returned." I drove the truck 7 miles next morning and started having same issue and check engine light flashing. Second trip to dealership "Random misfires stored in ECM 500 counts and lower refer to DOC 4630888, Fogged intake system added cleaner to fuel tank. Test drove 35 miles misfires did not return." Husband had asked about coil packs and they said they were "good". Drove it 4 miles this morning and it's misfiring again with light flashing, husband is out driving it right now on Expressway...WHAT COULD BE WRONG???? We've spent 600$ thus far and the problem is not fixed. Very frustrated!