Strange misfire
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Strange misfire
My old friend, my 2001, F250 with 6.8 liter V-10, is letting me down. I was going for feed and noticed a small misfire at idle. I drove the truck back home and it seemed to go away. The next day I drove to work (5 miles) and all seemed good. I was driving back home and noticed a misfire under load ( going up hill) and actually had to take it out of overdrive the rest of the way home. I replace the fuel filter. In tearing the filter apart I noticed what looked like mud in the pleats. The new filter made no difference. I drained fuel and removed tank. Tank was clean but sock in fuel pump looked plugged. Replaced the sock, installed the tank and drove to gas station (5 miles) truck ran great. Filled with fuel and started home and mis came back. Noticed I had a leak on the fuel pump tighening ring. Removed tank once agian to fix that leak. After reinstalling the tank, I drove it and it ran good (about 5 mile). Started back home and miss came back. Plugs were replaced 5000-7000 miles ago. Truck has 130,000 miles on it. No CEL on. Everything else seems to work. Any suggestions?
Cargo Master
Joined: Apr 2010
Posts: 3,274
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From: Seattle area
Get a code reader and see if it is throwing any codes. I ran for two or three months with a cylinder not firing, including towing 8k lbs over a mountain pass. I didn't get a CEL until one day running unloaded up a freeway onramp.
Btw - I had a failed ignition coil. I think they're not uncommon in older engines.
Btw - I had a failed ignition coil. I think they're not uncommon in older engines.
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Thanks for the reply.
What my confusion is the running good right after I have the fuel system drained. I guess a weak coil does make sense. Once the coil gets warm it could start acting up. But them again the mis was and is constant after each time I had the tank off but not before I drove it a few miles.
I was getting truck inspected for license and asked Ford Dealer to see if they could see any codes. They replied that they did a balance test and all was good. Of course the truck ran good for them but now the mis is fairly constant will ask them again. They did not charge me the first time to put on the machine but am sure they will make up for it this time.
What my confusion is the running good right after I have the fuel system drained. I guess a weak coil does make sense. Once the coil gets warm it could start acting up. But them again the mis was and is constant after each time I had the tank off but not before I drove it a few miles.
I was getting truck inspected for license and asked Ford Dealer to see if they could see any codes. They replied that they did a balance test and all was good. Of course the truck ran good for them but now the mis is fairly constant will ask them again. They did not charge me the first time to put on the machine but am sure they will make up for it this time.
Posting Guru
Joined: Mar 2005
Posts: 2,060
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From: Burnsville, MN
Not sure how well this would work for you, but there have been a number of posts from people who have spit a spark plug, and then were impressed at how well the the engine ran on only 9 cylinders.
If you only have one bad cylinder, could it work to sequentially disable one cylinder until the intermittency problem goes away? Then you'd at least know which cylinder to focus on...?
If you only have one bad cylinder, could it work to sequentially disable one cylinder until the intermittency problem goes away? Then you'd at least know which cylinder to focus on...?
Posting Guru
Joined: Mar 2005
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From: Burnsville, MN
By the way, I'm just throwing this idea out for consideration. But if you decide to pursue it, be sure to unplug the respective injectors so you're not dumping uncombusted gas into the catalytic converter....
Cargo Master
Joined: Apr 2010
Posts: 3,274
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From: Seattle area
I'm definitely impressed how well the engine runs on nine cylinders.
More Turbo
Joined: Jul 2009
Posts: 705
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From: Taxachusetts
mine turned out to be a randomly failing cop(s) which I let go for a while taking out my cat. never set a cel or a code
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How did you find which COP(s) it was? I had a vacuum gage on it last night while unplugging injector nozzel connectors and could not find which cylinder was kicking out. I also put an ohm meter on 8 (ran out of time to get to the back two on the passenger side) of the coils after I got the truck to missing and could not find one that read bad. Have an appointment to put truck on the scanner tomorrow. Has anyone tried the $12 coils you can find on ebay? I know you probably get what you pay for.
Thanks for the input!
Thanks for the input!
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Joined: Jul 2009
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From: Taxachusetts
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