Went to change my spark plans and decided to run the scope inside to see how the piston heads look. Lots of carbon buildup. She has 138k. I just purchased the car. Not sure what kind of gas the previous owners used. I'm guessing it's normal for these engines with direct injection to have carbon buildup? I just replaced the pcv valve since I read that can be a big reason for oil consumption, maybe some oil was getting in to the pistons because of a plugged up pcv? Anyway, I want to clean the carbon. What recommendations or suggestions do you guys have? I saw videos with some guys using Liqimolly valve cleaner in gas tank for a few cycles, few others used a cleaning solution over night and then used a hose to vacuum it out.

 

How magnified are those pics? the thrust sides of the cyl walls don't look good, crosshatch is normal.

 

I zoomed in quite a bit in those pics. What do you think? Try liqui moly valve cleaner?

 

I can't really help you there because I always check my vehicles out as thoroughly as possible before purchasing them, I'm not convinced that something you pour in the fuel tank or directly in the cylinders will cure the problem. If your car is using oil it's doubtful any quick fix will help.

 

If you just want to get rid of the carbon you can run water injection on a long trip, that will clean it.

 

There are plenty of liquid decarbonizers out there. They work to some extent. My biggest concern would be putting all that junk through the cats (the black smoke that comes out of the tailpipe is frightening)!