6.8L Help Needed !!!
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Joined: Jul 2019
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6.8L Help Needed !!!
I have a 2003 F20 Lariat 4x4 with a 6.8L V10 in it and it is acting up. I am getting code PO304. I have changed the number 4 coil pack(twice just to make sure I didn't get a defective one) and the number 10 coil pack just in case it was the fourth coil in the firing order and have replaced all of the injectors and the code is back. On a cold engine I sprayed it down with starting fluid to make sure I had no intake leaks. After I clear the code it will run for 60-110 miles before the code comes back. I am at a loss and everything I now do is chasing my tail. It's not like the code comes back immediately otherwise it would be easier to find the real issue. Fuel pressure is up and it just seems like a constant random (I know but it was the best way to describe it) misfire on cylinder four. Can anyone help or give me an idea as to where to look next?
Lead Driver
Joined: Mar 2006
Posts: 6,264
Likes: 438
From: IL
Did you try changing Spark plugs plugs or moving number 4 plug to see if it might be plug related or cylinder related?? Did you do a compression test? Is the p0304 the only code being pulled up? Did you check the wiring harness to make sure the injectors are receiving good voltage? These are just some thoughts..
Fleet Mechanic
Joined: Oct 2017
Posts: 1,704
Likes: 164
From: Southwest Ohio
There are multiple things that can cause a misfire. If you look at the short term fuel trims, see if you see a big increase when the misfire happens. If so, this is often the sign of a large vacuum leak, perhaps at the exhaust manifold. Since you're already swapped ignition components and no fix, you need to start diagnosing by looking at the fuel trims when running.
-- Dave
-- Dave
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