Misfire?
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Lead Driver
Joined: Mar 2006
Posts: 6,263
Likes: 438
From: IL
Misfire?
Hey everyone, I have a 2003 F350 5.4L 4x4 137K. Took it out yesterday and started misfiring or at least that's what it feels and sounds like, NO check engine light and when it's idling it doesn't misfire. Suggestions on the the first thing to attack? Cops? Plugs? Sensors?
Thanks
Thanks
Thread Starter
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Lead Driver
Joined: Mar 2006
Posts: 6,263
Likes: 438
From: IL
Thread Starter
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Lead Driver
Joined: Mar 2006
Posts: 6,263
Likes: 438
From: IL
I put my scanner on over the weekend, like I thought no codes presented. I changed the coil on Cyl 5 about a year ago, so I started looking at that, but found nothing unusual with it, I changed it out anyway, but it was still missing, I started un plugging the coils 1 by one figuring the dead one will show itself, but no love there either, pulled the breather blew on the MAF, ran rough for about another two minutes then all of the sudden it's running fine, so I have no idea what was going on.
Cross-Country
Joined: Oct 2017
Posts: 68
Likes: 0
From: Deep South
My truck will also randomly missfire and then clear it’s self up. If you can get it to do it again look at the fuel trims and o2 sensor data to track down which bank it is. It’ll show up as running rich because of unburned fuel. Once you have that use a IR thermometer and check exhaust port temps the one not firing will be cooler. Or slightly cooler depending on severity of the miss. When you have that start looking into the basics like wet plug boots from a leaky cross over or a drip from the hood. Iv seen them miss until the coolant or water evaporates and then it’s fine again. The coils will intermittently fail even though people say they don’t. Especially while hot. Look at the connectors for both coils and injectors. They get brittle over time and will break and lose connection intermittently as well. If you have a good scan tool you can make sure the injectors are squirting based on fuel pressure and manual fire of injector through the tool to confirm all the wiring and drivers are good. Provided you can get it to do it again. I’m still tracking my intermittent stumble to this day because it randomly does it and I can never get it to do it when convenient to check.
Thread Starter
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Lead Driver
Joined: Mar 2006
Posts: 6,263
Likes: 438
From: IL
Thanks for the Info Keeth, I'll keep my eye on it...I figured maybe carbon broke off and got caught somewhere, I only really use the truck to haul a trailer a few times a year or when one of the Bikes break down, I think I put a whole 500 miles on it last year.
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Cross-Country
Joined: Oct 2017
Posts: 68
Likes: 0
From: Deep South
No problem. If it’s any consolation mine seems to only do it if it’s been sitting for a couple weeks. Let us know if you figure it out.
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