Carbon on valves

T56MaxTorq said
Direct injection engines get this a lot. Even more with a turbo. So much that one engine had typical manifold type fuel injectors that ran at idle to clean the intake tract. Frequently, rev them up high for about half-minute to “excite” the valves and produce a lot of heat to wick any carbon buildup.

Do you use ethanol fuel?

I heard Toyota added port fuel injectors to their GDI engines at some point to keep the valves clean.

That engine looks like it was driven very slowly probably never more than 1/2-throttle. Also probably ran rich (I'd bet from an improperly-working choke) and/or had oil leaking down the stems and I wouldn't be surprised if the thermostat failed at some point but they just kept driving it and it never got up to full operating temp. Lots of drivers out their think it's bad for your engine to go WOT and without idiot lights most people don't even know what the temp gauge means or they think as long as it doesn't overheat everything is fine.

I know when I drive my brother's TDI (diesel) VW after my bros have been driving it a lot it seems just a tad down on power until I get it warmed up and floor it for 5+ seconds to burn out the carbon then it runs better lol. Neither of my brothers are gearheads or into cars at all so they have no interest in going faster than they need to whereas I'm a total leadfoot lmao.