I have F-250 with a 5.4 gas engine. It has the check engine light on witch says their is a misfire in both #1 and #8 cylinder. I changed the fuel filter, and also ran fuel injection cleaner on a long freeway drive. Also it was pinging, so I started using high octane gas, and this seemed to help. It seems as if the timing is advanced slightly to cause the ping. What test should I do first to diagnose the problem?
I will change the plugs, and check the coils. Thanks Kdzee
May, 17, 2013 AT 8:54 AM
Just giving everyone a follow up on what I did and the results. I changed the plugs and removed and cleaned all the injectors. I tested all the injectors, first by listening for a clicking sound while in operation. Then I removed them and submerged them in injector cleaner. I inspected all the O rings before reinstalling the injectors. I inspected all the coils and cleaned the contacts, they where green. I used a wire dryer to clean, and then put dielectric grease on all the electrical contacts. After everything was reinstalled, I reset the computer then just started driving for a couple hundred miles, the check engine light never came back on and the truck passed smog.