misfire in both #1 and #8 cylinder

2001 FORD F-250
175,000 MILES
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ANONYMOUS
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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?
Jan 26, 2013 at 1:25 AM
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ASEMASTER6371
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check the plugs and coils. do this first

additives for injectors rarely work.

carbon build up could be the pinging

roy
Jan 26, 2013 at 1:28 AM
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KDZEE
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I will change the plugs, and check the coils.. Thanks Kdzee
Jan 26, 2013 at 2:04 AM
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KDZEE
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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.
May 17, 2013 at 8:54 AM