2007 Superduty Misfire issue (solved for me)

[thenag]

If this should be moved to tow rigs, go ahead and move it. I am mainly putting this here so that it may help someone else out there, hopefully it comes up in the first few pages of their google search.

I have a 2007 Ford F350 Superduty with a V10 and a 6speed manual, 135,000 miles on it.

My father-in-law borrowed the truck and it started running really rough, he limped it back to his house. It had a MIL on. He has a really nice code reader and it had several issues mainly with cylinder #5. (of course the one back by the firewall). So for troubleshooting reasons I swapped #5 coil and plug with #7.

We started it, it started fine but then started to run worse and worse. We pulled codes, it still had P0305, (misfire #5) and now P0303 (misfire #3) and P0300 (random misfires)

My father-in-law and I googled around for probably about 30 minutes not really coming up with anything compelling. I was thinking it must be a wacky ass vacuum leak. My mother-in-law came out to chat and said something about the gas tank.
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A light bulb went off in my head

I un-screwed the gas cap and started the truck. It ran great. Cleared the MIL and it did not come back.

If you have a 05-ish to 07-ish Super Duty and drive in dusty conditions you probably have a Vapor Canister that is mostly plugged. They mounted it above the spare tire, you know a nice dust free place to put it. Usually you know this because when you fill up it will constantly trip the auto fill on the gas pump, and you will have to hold the gas pump handle in a strange way or pull it 1/2 way out of the truck to get full fuel flow.

So if you are having a total lack of power and random misfires, P0300, just try loosening your gas cap. Sounds strange as heck but it worked for me.

I have a new vapor canister ordered and will replace it this weekend.


Nathan

*Spark plugs have about 5000 miles on them, I got the original ones all out using the OTC 6918, it clamps down on the porcelain, I didn't break a single plug, they were original with 130,000 miles I recommend the OTC 6918*

 

[mbryson]

Interesting and good info. Thanks!

 

[thenag]

While driving today the MIL came on but it was a P0455, which is basically the code you get for driving around with your gas cap loose...

Still running great. I will have to take a scenic trip to Heber this weekend to get some miles and hills on it.

Nathan

 

[thenag]

I replaced the evaporator canister yesterday. I have only driven it a few miles we will see what happens.

Here is a picture of the old evap can, it sits above the spare tire and is is as wide as the space between the frame rails. (wrench for size reference)


There is a semi-ridgid plastic line that comes down the frame rail to connect to the canister. Don't cut that line it is expensive. I cut the old nipple off the old canister then used a big fuel line remover tool to get the connector off. (sorry I forgot to take pics) My dad says that he was able to force the connector off without special tools on his.