While cleaning the intake valve carbon build up, I was rotating the crankshaft and didn't hit the TDC (Top Dead Center) on one of pistons. That meant, the that cylinder's intake valves were slightly open, and it drained all the carbon cleaning fluid (Chem-Dip and Seafoam) that I poured into the intake valve chamber to leak into the combustion chamber (on top of the piston). Crap, but I used that opportunity to soak the piston top overnight. Next day, I vacuumed out the liquid out of the combustion chamber, and I was happy to find the heavy carbon had come apart. I then took it out for highway speed driving for about 30 minutes, and verified that most (90+%) of the carbon got cleaned (burned off). So I did the same for the remaining 5 cylinders, and now I have pretty clean piston, in addition to the recent intake valve cleaning. The car definitely feels more responsive. I'll do some 0-60 testing in the near future to validate this.

 

Again killing it with the videos and proving that soaking the tops cleans the carbon. Also by cleaning all that carbon, you will increase your mpg's.

 

That's awesome! It's hard to find advice for getting rid of carbon in our direct/dual injected toyota engines. might try this out on my gs350 awd that i'm sure is full of carbon internally

 

You know, you've been mentioning avoid doing 10K mile oil changes and doing it in much short interval like every 3K miles.
I've always try to follow the manual, but in this case, I think you are so correct.
I've been warming up to this idea and have been studying more about it.
As of today, I'm fully sold. I'm gonna immediately change to 3K-5K (max) oil change cycles.
Based on all the studies, maintaining good quality oil at proper level is critical in not seizing the piston oil control ring,
because once that fails, then cylinder wall damage and oil burning condition just accelerates downhill from there.

I need to measure my oil consumption more closely, but I think I'm losing about a quart every 2K miles,
but let me monitor all my cars closely and report back.

The Car Care Nut had best explanation on this.

 

Mine is 2006 so it's GDI only and that's why I had such heavy carbon build up.
Aren't GS350 dual injected? If you do open the intake manifold, I'm very curious to see what the carbon build up situation is.

Now that I know piston soaking works and it's easy to do, I may do this annually or every 10K miles.

 

YES, GS350's w/ 2GR-FSE's are all Dual injected, this has been corroborated by other posts and research from other CL Users. Apparently, the carbon issues are abated by this, but I still want to reach higher MPG's with '08 GS (Right now, I get highest 25mpg with cruise control on highways, and about 18 best in city driving, I have read posts about other users getting closer to 31-35 on highways with their same year and model GS's and it make me quite jealous haha)

Best, Norm