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?

 

1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

Might want to move this to a more appropriate section or forum. To save lot of time you may need a new engine. It sounds like you have a path for coolant to enter the combustion area of the head. So possibly a head gasket could solve it. Or you may need a new head. You could have a crack in the block as well.

 

Yes sorry for being off topic. I'm somewhat familiar with this board and wanted to get advice from people I trust.

Man you really don't want to hear that about a vehicle you make your income with. Like I said since I blew the antifreeze out of the plug well it's running somewhat ok, although still missing. This car does about 500 city miles a week and although I don't want to I'll probably keep using it until something happens or I figure out what to do about it. Should I put some kind of stop leak additive in to try to buy some time?

How do I investigate this to figure out what I've actually got here? If it's just the heads or the head gasket I'll probably just replace, but if it's the block I guess there's no choice other than replacing the engine.

 

I've now gotten information that this 4.6 engine is very prone to having the intake manifold crack or gasket fail. What test could I perform to make sure it's either my intake manifold or gasket that's leaking before I start taking parts off?

 

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.