2007 Mercury Milan PCM? Coil?

The mechanic said the pcm died and melted the #4 cylinder coil. Quoted me $2600 for repairs! I called the dealership, they said the 8/80 warranty would cover the pcm and save me $1000 but have to pay for the tune up portion. The mechanic suggested I get them to cover it all! To be continued! Thank you.

I just went through and experienced this nightmare, but I think it's partially my fault.

My wife was pulling out of our driveway and as she shifted into drive, the car basically lost all power and started to stall. I was able to get it to run long enough to pull it back into the driveway and put a code reader on it. There was P0353 code meaning that COP C was failing. That, of course, is cyl #3 and under the intake.

I bought 3 new coils and 6 spark plugs because if I had to pull the intake, I may as well to do a tune up and replace all of the hard to get at coils. Got it all back together and then the problem moved to cyl #5 (P0355). I swapped the front coils to see if it moved. Nothing. Same thing. Swapped plug locations. Same thing. I replaced the connector for COP E. Still, the same thing. Then I just unplugged COP 5 and it moved to cyl #1 (P0351). Plugged E back in and it stayed on (P0351). Pulled the intake, swapped COP A with COP B. Still stayed as a P0351. I bought 3 more coils and replaced front 3 thinking maybe it prefers that the coils all be the same. Still, same code.

I was wondering if the Iridium spark plugs I got were the problem, so I got platinum plugs like the stock ones. As I was going to put them in, I pulled COP C and it was totally melted. Crap, at this point I knew that the computer was fried. I pulled the computer and sent it to circuitboardmedics and they turned it around in a day. In order for their warranty to be honored, I had to buy 6 new coils. Another $630.

Now here is what I think is important. New coils come with dielectric grease applied at the opening to the rubber boot. This is convenient, but is something I think that may have caused the failure. You think "wow, I can just pop these on." When you do, that grease gets all over the terminal of the plug. There's only a spring that connects with the terminal when the coil is on the plug. That will create more resistance to the plug and possibly blow out the coil. When I pulled the #1 and #3 plug, I noticed the grease all over the terminal.

When I installed the newest coils, I made sure that I smeared the grease around the inside of the rubber boot so the grease will only be contacting the insulator of the plug. I also made sure that all of my new coils had the grease in the same place. One of them actually looked like it was already used. The grease was on the spring, too. I returned this to make sure that I got a brand new coil. Considering the issue, it's a good chance that a prior customer having the same coil problems could have returned a faulty coil.

Anyway, after repairing the computer, 6 coils and spark plugs, all is good. I think the key to remember is that the dielectric grease should be spread evenly and thinly before putting it on a plug to ensure there is full contact between the plug and the spring in the coil.

This is just my guess, of course, but I think it's something that should be considered when doing the job yourself. I can see mechanics even doing this incorrectly.