My 2012 MKZ has thrown a P0306 over the past couple of weeks. I cleared the code and then replaced all of the plugs with factory Motorcraft plugs; set at 0.054 in gap, per Lincoln. NGKs were formerly in there, but they looked okay. They didn't look fouled or anything.
So, the car runs okay for a couple of weeks and then we got a cold snap here in Colorado and bam, the P0306 code goes off again. I don't know if the cold had anything to do with it or not. So, I go to Advance Auto and pickup a new Motorcraft coil pack, figuring that it was either the plugs or the coil pack.
It is still pretty cold here today (22*F) but I replaced the #6 cylinder coil pack. I already cleared the code before I worked on it. So, I start it up and it is immediately idling rough and sure enough, it throws the P0306 code again. I made sure to push in the coil pack plug until it clicked. One thing I will say is that the former owner pretty much broke off every one of the locking tabs (red tabs on the connectors). <rolling my eyes> So, I pushed all of them in the best I could and hoped they clicked into place.
Any thoughts on now what to look for to fix this stupid P0306 code??? I don't believe I have the firing order or the cylinder order incorrect for the 3.5L Lincoln V6 engine. Upon my research, I have read/heard that the P0306 relates to the actual cylinder number of the engine and I have read/heard that it relates to the 6th cylinder in the firing order. However, for the 3.5L V6, the 6th cylinder in the firing order is cylinder #6, so I'm pretty sure I have the right cylinder that I'm working on one way or another. It is the driver's front cylinder. 1-2-3 in the back (pass side to driver side) and 4-5-6 in the front (again, pass side to driver side).
Only other thing I can check is to possibly see if there is some sort of broken wire and/or the connector is bad. I don't know what else it could be. I guess a vacuum leak, but from where? Intake? And if so, why is it only triggering the #6 cylinder misfire?
Is there any way to test the coil packs? My luck I got a bad coil pack from Advance Auto and that is continuing my issues.
Any help would be truly appreciated. I'm getting frustrated with this thing.