Keep getting Number four miss fire CEL
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Mountain Pass
Joined: Dec 2003
Posts: 197
Likes: 2
From: Onalaska WI
Keep getting Number four miss fire CEL
I have 2010 ford super duty with 5.4 engine in it with 210,000.00 miles. We have change the COP, and all the spark plugs, the mass air flow senors. we also moved COP and injector to different cylinders. trying to solve problem.
Dose anyone have any other ideas why it keeps throwing CEL.
Dose anyone have any other ideas why it keeps throwing CEL.
Fleet Owner
Joined: Aug 2010
Posts: 21,253
Likes: 1,656
From: Reynoldsburg, Ohio
Having already changed everything else associated with #4 I'd suspect the COP connector from the wiring harness. Occasionally during a plug change the locking tab is broken and it no longer stays fully engaged. NAPA EC259 is a good choice for a new connector if this is the problem.
Fleet Owner
Joined: Aug 2010
Posts: 21,253
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From: Reynoldsburg, Ohio
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Mountain Pass
Joined: Dec 2003
Posts: 197
Likes: 2
From: Onalaska WI
yea checked plug in and it is connected with the tab in place did not re place because it look all right
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Fleet Owner
Joined: Aug 2010
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From: Reynoldsburg, Ohio
Just because something "looks right" doesn't mean its working properly. In this case the COP connector has a locking tab intended to maintain a tight electrical connection---its under a bit of pressure in fact.
Sometimes those tabs can/do break and cause the COP connector to loose contact. Occasionally this is a sporadic thing, other times its a constant loss of contact that resembles a failed COP or plug.
While the vehicle is running gently manipulate the #4 connector and see if it has an effect on engine idle. Tugging on it GENTLY or pushing it into the COP is another way for this sort of test.
Because you've already done a number of other things but not paid attention to the connector ruling it out is just a smart move.
Thread Starter
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Mountain Pass
Joined: Dec 2003
Posts: 197
Likes: 2
From: Onalaska WI
Having already changed everything else associated with #4 I'd suspect the COP connector from the wiring harness. Occasionally during a plug change the locking tab is broken and it no longer stays fully engaged. NAPA EC259 is a good choice for a new connector if this is the problem.
Change wire harness with NAPA EC259. And guess what today though code p0304 Again!
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Mountain Pass
Joined: Dec 2003
Posts: 197
Likes: 2
From: Onalaska WI
No did not check the compression. But all so i dose not throw code right away can take 5 days to 2 weeks. if it had bad compression you would think it throw a code right away!
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