cyl 7 misfire and coolant in the plug well

My '11 Crown vic with 270k miles suddenly started running rough mostly at the lower end of the gears. By the time you got into o/d the whole car shook. Scan tool gives me P0307 cyl 7 misfire, and P0316 misfire upon startup. So I pull the coil on 7 to find a pool of burnt smelling coolant about 2" deep. Siphoned and blew it out and removed the plug to find it's electrodes fouled with a thin coat of something shiny and black. Rubbed off without much effort. The plugs are about 4 weeks and 1500 miles old. Pulled cyl 6 coil right next to it and found a lot of white particles about half the size of rice stuck to the sides of the plug well walls. Seemed odd as I'd just blown out all the plug wells a month ago. Blew it out again and removed the plug to reveal electrodes that were coated slightly white. This plug had a ring of a black just south of the hex part. Looked like darkened sort of coagulated oil. Wiped off easily.

The car drives much better now after blowing the antifreeze out of the plug well but the miss is still there. So glad as this might buy me some time to get this figured out.

I'm not even sure how it's possible for coolant to get in a plug well. Any ideas, head gasket maybe? What's my next step in investigating?

Not a jeep so hard for me to say.
But if you have a leaky head gasket you will have steam coming out of the exhaust. Look for a crack in the head. Be sure to add coolant and burp out the bubbles . If you see a constant stream of bubbles with the engine running likely cracked head.
Many coolants glow in a black light. So you might be able to track it down.


Regards,
JPNinPA

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Thanks for the advice JPN.

I've also been advised that this may be a leaky intake manifold or gasket. Is there a test I can perform that confirms it's my intake manifold that's leaking before I start taking parts off?

I think the green antifreeze fluorescent in black light. You could start with a cheep Halloween black light. Then add the dye if the coolant isn't fluorescent by itself.
Just be sure to look ig the coolant got into the oil.


JPNinPA
Using Jeepz.com app

Found the leak at the front driver side corner of the intake manifold. Really wish it wasn't so cold out now.

Any last advice on an inexpensive source for an OEM intake mainfold? Considering how much this car is driven I better stay away from after market.

Junkyard?


Regards,
JPNinPA

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Depending on the size and location of the crack, JB Weld might​ be an option. You'd need to clean the crack up real good first!