So last December I finally got around to finding the source of a random misfire that would come up maybe 6 times a year. The Expy idled fine, had plenty of power, and generally behaved normally. But that darn misfire, only under load at highway speeds, was nagging. Finally I decided to pull all the plugs to just see. The previous owner had said they were all swapped, at unknown mileage, so i figured worst case was I would find out immediately if that was true. Sure enough they all came out smooth as butter and this BEAUTY was waiting for me in cylinder number 4. Just look at it:
![20231210_155419[1].jpg 20231210_155419[1].jpg](https://www.expeditionforum.com/data/attachments/79/79944-a01696b2fe2641d4d5a20021f7c5b3bf.jpg)
Remember this was running JUST FINE 99% of the time. All the plugs were E3 diamond fire's, all looking worn out, but none so spectacular as like cyl 4.
So I changed all the plugs with an Autolite replacement. This was December 12th. Now about 8 months later it starts to misfire again. The scanner says cly 4 but the power balance test isn't so conclusive. The very enjoyable task of pulling #4 yielded this:
![20240729_210019[1].jpg 20240729_210019[1].jpg](https://www.expeditionforum.com/data/attachments/79/79945-8103aba333324cee20050a5a6cbfdb79.jpg)
Soooooo, does anyone have any idea why the engine would be destroying this specific plug? Is it just a fluke and my catalytic converter was craving some spare metal chips? Is my stock coil just too powerful for the cheapo autolite plug?
Note the engine has no noticeable coolant leak, all injectors were refreshed last year also, and no codes are being thrown for anything. 116,*** miles, 2006 Limited 4x4. Tonight I also changed the coil on #4 to a spare I had just incase.
![20231210_155419[1].jpg 20231210_155419[1].jpg](https://www.expeditionforum.com/data/attachments/79/79944-a01696b2fe2641d4d5a20021f7c5b3bf.jpg)
Remember this was running JUST FINE 99% of the time. All the plugs were E3 diamond fire's, all looking worn out, but none so spectacular as like cyl 4.
So I changed all the plugs with an Autolite replacement. This was December 12th. Now about 8 months later it starts to misfire again. The scanner says cly 4 but the power balance test isn't so conclusive. The very enjoyable task of pulling #4 yielded this:
![20240729_210019[1].jpg 20240729_210019[1].jpg](https://www.expeditionforum.com/data/attachments/79/79945-8103aba333324cee20050a5a6cbfdb79.jpg)
Soooooo, does anyone have any idea why the engine would be destroying this specific plug? Is it just a fluke and my catalytic converter was craving some spare metal chips? Is my stock coil just too powerful for the cheapo autolite plug?
Note the engine has no noticeable coolant leak, all injectors were refreshed last year also, and no codes are being thrown for anything. 116,*** miles, 2006 Limited 4x4. Tonight I also changed the coil on #4 to a spare I had just incase.