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?

 

Hmm... I can't think of much similarity between a 2011 Ford Crown Vic and an AMC/Chrysler Jeep XJ that ended production after the 2001 model year. I guess they are both vehicles that the U.S. federal and state governments have purchased for police and other official uses...

If the coolant was -outside- the engine (meaning just in the recess for the plug), then it probably got there from a leaking hose nearby (best case) or possibly a crack in the head or block if there's a coolant passage nearby. Put a coolant pressure tester on the system (free loaner tool from your local parts retailer) and see if it starts blowing antifreeze out somewhere.
As far as the misfiring - you need to test the coil packs (google it) and see if one or more is bad. I'd say the primary suspect is your antifreeze soaked one. What did googling the codes with the YMM indicate? Typically there's a sort of consensus of what code X means for vehicle Y and what the most common fix is for the problem.

 

If you check the intake manifold you will see that the gasket is leaking coolant , the manifold has coolant front and rear of the manifold .

 

Thanks for the help guys.

After blowing out the plug well the car ran much better although still had the mis. Ignition coil tested ok at the car store. Misfire on cyl 7 is what the code indicated, which is where the coolant was.

tech Is there a test I can run to make sure it's the intake manifold that's leaking before I take everything apart?

 

If you can pressurize the cooling system you will see it leak where the intake and the head meet . I work on police cars we change intake gaskets and manifolds all the time the 4.6l engine always leaks there when the plastic in the manifold and gaskets gets old . so when you get the manifold off check it over where the gasket and manifold meet .

 

Sorry to have upset some of you although I do appreciate your help all the same. 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.