i think I’m having valve carbon build up issues. there is a #2 misfire I swapped coils, cleaned and regapped the spark plugs, did a compression check 147 PSI dry, replaced the fuel injector and tryed cleaning the intake. Cheaning the intake helped alot but it still is a issue..... anyone have any ideas or do I really gotta pull it all out...

 

I've just joined the forum, but I've seen Seafoam used for this issue. Don't take my advice yet, I'm still very new to the MINI world. Meanwhile, there are YouTube videos on the fogging process. I'll follow your progress.. Keep us posted

 

The best way to deal with the carbon buildup is to walnut shell blast the back of the valves. Lots of how to's here and YouTube. You can buy the tool on Ebay.

 

i have called the dealer ships and they said it is physically impossible to get carbon build up on the n18 motor which I have but I do have no cats and a few other mods so I’m pretty sure I do have build up

 

You can try Techron. Get a bottle and use according to directions on the bottle. Be careful. The bottle may be intended to treat way more gallons of gas than your car's tank holds, so don't just dump the whole bottle in the tank.

Shake the bottle a bit then pour in the right amount of Techron, then fill up the gas tank.

While the engine doesn't have port injection and the valves thus don't get sprayed with fuel, the valve timing is such that some combustion gases flow back and can flow past/around the intake valves in which case the Techron can do its thing. But it may take a treatment or 3.

Do a treatment. Then have a look and compare the current state of the valve deposits to what they were before you used the Techron. If you see any improvement repeat the treatment. And maybe even a 3rd time. Afterwards change the oil/filter. The Techron can increase contamination of the oil and you can only remove that by draining the oil and replacing it with fresh oil.

If you see no improvement after the 1st Techron treatment I'd still give another treatment a chance. If it does work it is much better than having to remove the head and have the deposits removed by some other process.

 

Here is carbon on the intake valves.


If the picture you posted is your valves they are pretty clean

 

The only way to get it real clean is walnut blast. None of those chemicals you use will save you from it. I've tested the treatment method with all possible products at Advance Auto and Autozone, none will come close, even after days of soaking and scrubbing with brushes, I can get a good portion out, but just not all the way clean like you would get from walnut blast. That's why I invested in a blast kit and so far so good, it's a breeze getting it done and it definitely improves the performance and gets away with any issues arising from that carbon build-up.

 

No fuel treatment will clean your valves on an GDI engine. Just remember that. They need to be walnut blasted.

 

I removed my intake manifold to replace the coolant crossover pipe. While in there, I took some pics of my intake valves after 155K miles. This is also a N18 that just had CRC GDi intake cleaner applied a week before.


So it seems those off the shelf GDi cleaners do little to remove carbon buildup. Especially if you have high mileage.