cyl 7 misfire and coolant in the plug well

[bradleyheathhays]

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?

[AussieinNC]

The spark plug issues with these Ford engines is well documented, as is the coolant loss thru cracks in the head adjacent to the plug itself...

Simplest way to repair it is a replacement set of heads...with the revised helicoil style inserts installed.

Put another engine in it or grab another daily....

[bradleyheathhays]

Man ok couple questions.

- Would you suggest using some kind of stop leak additive to buy a little time here?

- I'd like to fix the problem the right way, but probably the cheapest way possible. Could you explain a little more why replacing the engine would be a better option than just replacing the heads?

[clay68c10]

Those engines didn't have the head problems. You have the 4.6 Mod motor. I work on police cars and these motors are incredibly durable.
Your intake manifold is probably leaking at the sealing surface to the heads. Coolant goes from the leak area into the plug wells.
A new intake manifold and seals will take care of the leak. Get new plug boots for the misfiring cylinders.
Check the heater bypass tube in the intake valley when you have the intake out. It is probably ok, but worth a close look while you are in there.

[95 S_Trucker]

Cylinder 7 is the second cylinder from the rear on the drivers side(on a ford at least)

The coolant passages are at the front of the manifold on the 4.6

Are you sure it's not rain water that got in from the outside? It can look pretty gunky/brown if it ran off the engine. You may need some new coil boots to keep water from getting in the spark plug tubes.

[clay68c10]

I have seen the coolant flow all the way down on both sides and get into any of the plug wells. The cops really run them hard till either the AC or heat quits working.
It could be rain water, but those intakes are the weak point on the 4.6. It's the first thing I'd check.
I'm with 95 S Trucker, at 200k+ I'd replace the boots anyway.

[95 S_Trucker]

I didn't read your post the whole way. You already said to check the coil boots.

Anyways, its funny, I work on my local police dept. cars. They don't have any of the v8s any more. A couple ecoboosts and a few 3.7s. I've had fun doing those water pumps.

[clay68c10]

We still have some Crown Vics left over. I just did an intake last week.
The Explorers aren't great, we have the 3.7 non turbos and a few vans with the Ecoboost. We're getting some Tahoes this time around, hoping they hold up.

[bradleyheathhays]

Thanks for the good news. I was really not looking forward to replacing the entire engine. Just got the vehicle but yes I'm pretty sure I have the 4.6L. My VIN is 2FABP7BV1BX107672 if you know of a way to cross check.

I kept what came out of the plug well in a clear plastic cup and from the side it looks exactly like slightly watered down coke. But between your fingers it feels right on 50/50 antifreeze. Smells burnt.

Clay is there a way i can test to see that it's definitely the intake manifold that's leaking?

[clay68c10]

The 4.6 is the only engine choice for that car.
You can pressure test the system, or warm it up till it's hot and look for the leak. It will be either corner in the front or the passenger rear.
If you have the old-style intake with the plastic front crossover, it could be leaking anywhere behind the alternator.
If you don't find a leak, keep driving it and keep an eye on it.
If it's seeping it will eventually leave white chalky/crusty stains in those areas.
It is possible that the PO just did an intake to flip the car and the coolant was in the plug well from then.

[bradleyheathhays]

Ok thanks I'll start working on it per your advice

[bradleyheathhays]

Thanks for helping a stranger everybody. Found the leak at the front driver corner of the intake manifold. Really wish it wasn't so cold out now.

Any last advice on a cheap place to get a OEM intake manifold? Considering how much this car is driven I better stay away from after market.

[clay68c10]

No problem, happy to help.
I've been getting stuff from Summit lately, they are willing to match prices and shipping is free over $100. Not sure if they have the OEM part but it's worth a look. Rock Auto would be my next thought.
I'v heard the after market intakes for those aren't great. Good idea to get a Ford one.

[clay68c10]

One left on amazon
https://www.amazon.com/Ford-9W7Z-942.../dp/B001H2R5HQ