Misfire/Overheat Issues

[Austin Hanischuk]

First time poster but I need some help.

2012 6.2L N/A with 122,000km.

I’ve had the truck for nearly 2 years now and up until 6-8 months ago it was a dream come true. As of lately though I’ve been chasing a cylinder 8 misfire (P0308) and misfire at startup (P0316), and on top of that I’ve had overheating issues to the point where the gauge will max out and I have to sit for a few minutes to let it cool off.

Replaced in the last 6 months:
All 16 spark plugs with NGK Iridium
Yellow top battery
Rad cap
Thermostat
And other miscellaneous parts that have nothing to do with spark/cooling.

I’ve tried swapping injectors, coils, and spark plug wires from 8 to 6 and the problem is always in cylinder 8.
Yesterday I checked the DS bank for compression and had
#2-196psi
#4-196psi
#6-184psi
#8-188psi
I know it fluctuates a little but figured 10psi wasn’t enough to cause a misfire.

I’ll add that the P0308 only comes on after the engine has been sitting for more than 8 hours, and I’ve never had it come on during the day, only after I finish my evening shift at 11pm.

ANY suggestions will be strongly considered so please throw anything at me as this has been a 6 month battle and I’m starting to lose faith lol

 

[pat247]

You have done a good job trouble shooting the problem so far. It may be time to bite the bullet and let a professional diagnose the problem. In my opinion the first thing you need to address is the overheating problem before it causes a bigger issue. It's possible the head gasket is leaking coolant into cylinder 8.

I hope you get this sorted out soon so you can enjoy your Raptor.

 

[MTF]

Are the spark plugs gap is correct?
If the gap is too far opened or a plug is damaged or defective it will blow out the spark under compression.

I agree, time to bring it in to the dealer.

 

[Austin Hanischuk]

Are the spark plugs gap is correct?
If the gap is too far opened or a plug is damaged or defective it will blow out the spark under compression.

I agree, time to bring it in to the dealer.

Yup! Plugs are all gapped properly. I’m going to be pulling the plugs on 8 today and checking/swapping. Maybe I dropped one and made a hairline crack in it or something. I’m kind of running out of ideas now.

 

[Austin Hanischuk]

I’m hoping the overheating is being caused by air in the system because it wasn’t filled up entirely when I did the thermostat so I’m going to try topping it back off now and see if that does the trick.

 

[MTF]

When it was over heating, what were the fans doing?

It should have been so loud you can hear them in the cab at speed, if not something is wrong for sure.

 

[Austin Hanischuk]

When it was over heating, what were the fans doing?

It should have been so loud you can hear them in the cab at speed, if not something is wrong for sure.

Yeah fans were running loud and proud. Ran it with the rad cap off to work out possible air trapped in the system and added roughly 4L of coolant/water mixture. I did the thermostat about a month ago so if it burnt 4L in a month I would’ve seen signs of it coming out of the tail pipes so I’m pretty certain it’s not getting into the combustion chamber.

 

[1BAD454SSv2]

At this point may be worth pulling valve cover to look at valve springs #8 cylinder may have a broken at top or bottom . If your using coolant with no visible signs of leaking your burning it. You can get coolant tested for combustion gases. or pressure test coolant system.

 

[Austin Hanischuk]

So I decided to order a new head gasket as I couldn’t see the issue being caused by anything else and low and behold my head gasket was cracked on one of the layers between cylinder 8 and the coolant jacket.

Had the head machined by a shop and put it all back together and now she starts and idles like she’s supposed to