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Cylinder Misfire


Cardinal

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Did you get a CEL? Google of Ford P0300 shows this:

 

http://troubleshootmyvehicle.com/ford/4.6L-5.4L/how-to-diagnose-misfire-codes-1

 

I misfire is usually pretty obvious if it is persistent. Did you clear the codes to see if it comes back?

 

I'd head to a dealer asap. I'm not sure it is safe to drive very far or very fast.

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A plug that is fully closed against the center is not a good thing. It doesn't look like it hit the cylinder though since the outside is still right. Don't regap the plugs you have get a new set. If there are any more that look like they've closed up then get thee to a dealer.

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I have read posts by owners on SVTPerf.com quite often where spark plug gaps have gotten closer after a period of time. The owner will gap his new/correct for the application plugs at .32 or .35, and a few months later develop a misfire and when the plugs are removed and checked, all are in the .22 to 28 range when measured with the same gauge. I have never read where someone has had a gap completely close, but "if" for some reason the gaps are closing over time, as experienced by the owners I mentioned above, could the gap completely close?

 

What would cause the gap to get smaller to start with? Cylinder pressure would not do this? would it?

 

I had a misfire on my Super Snake (no code, just running rough) about a year after I got it back from the Mod Shop, I pulled the plugs, all averaged .25 to .28. The NGK TR6IX's had been installed by Shelby for the KB, the recommended gap is .32. Why were mine .25 to .28 with approx. 400 miles on the car? <<<Do these plugs really close up over time and with use?

 

 

 

 

 

R

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:doh:

 

Take all the plugs out and re-gap them!

It's not help

 

A plug that is fully closed against the center is not a good thing. It doesn't look like it hit the cylinder though since the outside is still right. Don't regap the plugs you have get a new set. If there are any more that look like they've closed up then get thee to a dealer.

Somethingis happen in cylender - spark is hited

 

Any resolution?

No, I wait a service...

 

I would suggest getting that cylinder "bore scoped" immediately.

Sure, I try to find. I'm realy don't know what the f@c. is happen on this time, some people say it can happen becouse of part of piston after detonation is hit spark...

 

I have read posts by owners on SVTPerf.com quite often where spark plug gaps have gotten closer after a period of time. The owner will gap his new/correct for the application plugs at .32 or .35, and a few months later develop a misfire and when the plugs are removed and checked, all are in the .22 to 28 range when measured with the same gauge. I have never read where someone has had a gap completely close, but "if" for some reason the gaps are closing over time, as experienced by the owners I mentioned above, could the gap completely close?

 

What would cause the gap to get smaller to start with? Cylinder pressure would not do this? would it?

 

I had a misfire on my Super Snake (no code, just running rough) about a year after I got it back from the Mod Shop, I pulled the plugs, all averaged .25 to .28. The NGK TR6IX's had been installed by Shelby for the KB, the recommended gap is .32. Why were mine .25 to .28 with approx. 400 miles on the car? <<<Do these plugs really close up over time and with use?

 

 

 

 

 

R

In all cylender 10, in this #6 is go down in heated temp is 6... in cool is 7...

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Either the plug is too long or the piston is somehow loose. Closing up a plug like that requires some type of physical striking. The only other thing I can think of is the possibility that the plug was "Blown out" sometime in the past and retapped in such a way as to lower the plugs normal position

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That is a strange one for sure, something you definitely need to sort out asap.

Here is a photo of one of my original oem Ford Motorcraft plugs that the car came in my 08 GT500.

The thread count looks to be the same, about 10 full threads (and 1 partial at each end).

My plug is 17mm from the bottom of the seat taper to the end of the threaded portion, and 22mm overall from the bottom of the seat taper to the outermost tip.

The only noticeable difference that I can see is the size of the electrode tip, the ones on mine are a fair bit smaller.

That has no bearing on length/reach of the plug though.

OEM Plug.jpg

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OUCH! That raises some questions. I'd expect that piece of aluminum bouncing around in the cylinder would have made some noise. I wonder what the underside of the cylinder head looks like? Where did the chunk of piston go? I'm surprised the piston damage didn't show up on the borescope inspection. I don't see detonation damage on the top of the piston other than the broken off piece. I'm used to seeing detonation damage in the center of the piston.

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