I heard about the crushed walnuts, but how they get them into where the valves are ? Through the air intake or some other way ? And as to how often to clean them, a lot would depend on how bad they are. But I would probably suggest every 25K miles or so (like maybe every 2 years, depending on how much mileage is put on) and a lot depends on gas and oil quality.
This and the brush method are the two most common, and most effective ways to clean them. There are several factors that lead to this, and using a full synthetic engine oil is one of the better ones. This reduces the rate and severity, but does not prevent it. The example I posted of the new 2015 GDI Corvette the owner is an aircraft engineer/tech and he broke it in hard (the proper way) and drained the factory fill of cheap DEXOS syn blend out before 500 miles, and has only run a premium full synthetic since so his are far better looking that others at that 20k miles mark. To do these you must remove the intake manifold and first blow all clean with compressed air so no road debris can enter the ports. Then wipe each port clean and then tape off any ports that the valves are not fully closed in. Then you can start by first using a long shaft flat blade screw driver to scrape loose all you can. Then use the CRC spray cleaner or similar (Seafoam, BG, AMsoil has a good one, etc.) to soak that port and valves. Let sit for 15-30 minutes to soak in and loosen the deposits. They are very hard and abrasive, so hard to remove. Then brush using a universal shotgun cleaning brush set (extension clamps in cordless drill and works well for DIYers). Once those ports are all brushed, you suck out the solvent and debris with a shop vac on the port and further with compressed air nozzle. Repeat 2-3 times depending on severity of the coking. Then once all debris and solvent is sucked out and clean, rotate engine until the ports not cleaned are where the valves are closed (usually only 2-3 movements will cover all valves) and then tape over cleaned ports (you must ensure no debris falls into the cylinder) and repeat. To rotate engine, a manual trans you can push on it in gear and it will bump rotate the engine. If auto trans, get a socket or offset box wrench on crank bolt and do so that way. If you want to try and do it with starter, make sure all coils are unplugged so it does not start as injectors spray fuel directly into combustion chamber and it mat start w/IM off.
Here are two of the better videos on doing this:
https://www.youtube.com/watch?v=NnMhNXXawjk
https://www.youtube.com/watch?v=7Pz0zTQ1bz0
Sounds like a dealerships' best dreams come true. Now in additional the "fuel injector service" they can upsell intake valve cleaning!
So all the money you "saved" by DI offering better fuel economy is instantly negated by needing a new maintenance procedure....ironically to ensure good fuel economy! LOL
I agree to a point, the dealers are charging outrageous amounts and they are using the solvent based that at best removes up to 40% of the deposits, but this also causes damage to the pistons and cylinder walls due to the hard crystalline abrasive nature of these GDI deposits. This is not the soft carbon of days past. The sales side does NOT want any consumers to know about this as it would hurt sales understandably, and the automakers all claim they have no issue (even BMW and GM, the worst offenders), and then claim they have "cured it" when they are still saying they have no issues with it while neither is true.
The more I read about this "issue", the more overblown I believe it to be. Aside from some notorious Audi/VW DI designs which were highly problematic, most other DI engines do not seem to exhibit measurable symptoms over time. Ford and GM have had DI engines in the pipeline for quite a while now, and many of those engines are in excess of 100k miles, and there does not seem to be any type of widespread maintenance requirement for their DI motors. Do they visual exhibit a higher carbon deposit than port fuel injected motors? Probably yes. Is it an actual problem that and end user is going to have to spend money to fix? Probably no.
Many good articles out there regarding this. I found this one informative:
http://www.autoguide.com/auto-news/...a-problem-with-direct-injection-engines-.html
I'd still love to hear an educated response to the catch can question.
The article, and many more all quote the auto makers that claim "we have no issues with this" when all automakers do. Think yours does not? Take the few minutes to remove your intake manifold and see in person, you will be shocked to see how severe. But most as the degradation is gradual as the coking forms will never realize it and will trade their vehicle for a new one passing on the problems to the next owner. Also, port injection engines due to the constant spray of detergent fuel on the valves that keeps them clean and cool, have zero issues with this. You would have to go back to carbureted engines to find intake valve coking issues, and they were far from this serious, but still wore out valve guides and the average gasoline engine used to need a valve job by 50-70k miles back then. So it has been several decades since there has been any intake valve coking on gasoline engines. This is an issue unique to GDI engines, and none are immune, and none have a "fix". Only installing a properly designed catchcan system will prevent this, and only a few are actually effective. 99% plus allow more oil and other contaminants pass through them and do little than make the owner "feel" like they have taken steps to prevent it. To date, only the Elite E2-X, Colorado Speeds, and the genuine RX systems stop all of this. And then there will always be a small amount of coking (the can systems mentioned stop 95% of the coking) due to the EGR emulation of the variable valve events that allows some back fill of burnt gasses that make contact with the valves backsides.
One only has to inspect their own valve to see, and also, BMW on the Mini has now changed the intake manifold from the rear to the front of the engine to make removal much easier than before on the prior mini models.
Lots of studies, with my favorite being a BMW tech that took his new BMW and every year at the same time had a dyno done on same dyno, same correction factors, every year for 3 years to document how much power was lost (first dyno was a year from new) and then performed the crushed walnut shell media blast method (many BMW dealer have these). Study this 3 year test:
See how the scale of degradation in power is not linear, but as time goes on, and miles accumulate, the deposits form more easily on the rough surface VS the new valves clean surface. Also, here is a port injection engine with 142000 miles on it, and no top tier fuel used and never a cleaning:
Anywhere the fuel made contact is deposit free from the standard detergents required by law in all gasoline.
Now, no oil is entering from the guides and valve seals unless the guides have already worn to the pint of valve instability that will allow oil past the seals. This rarely occurs until 20-30k miles on the engines. With port injection it was unheard of to ever have worn valve guides unless a mechanical failure like the LS7 GM engine with titanium valves. The heads were machine slightly of square, and the repeated impact with one portion of the seat before the rest of the valves placed side loads on the valves wearing the guides. Other than that example, guide wear went away with the carburetor.
All of this comes into the intake air charge with the PCV vapors. So trapping and scrubbing these vapors of the oil mist and other compounds that cause this will prevent it. Valves, unlike pistons that can maintain coatings for wear, etc. valves operate now so hot that there is no workable coating solution. The valves cannot operate any cooler w/out reverting back to port injection (the added small supplemental port injectors Audi and Toyota use does little, but does help a small amount, bit then allow more incidence of detonation).
Instead of posting hundreds of pictures as examples, here is a link to pictures supplied by automotive techs around the World of almost every make you can imagine, and you can see none are immune, yet all claim to be:
https://www.google.com/search?q=dir...k6XKAhUIrD4KHc3hBdMQ_AUIBygB&biw=1600&bih=775
As I work on these engines daily as my career, I can state there is NO automaker that does not suffer from this, and all are suffering from this. Anyone doubting this, take your IM off and see for yourself. Live in FL near Tampa/Sarasota? PM me and I will make arraignments for you to come to a shop that does the cleaning and they can do this for you if your not comfortable with removing your own IM. Especially anyone that thinks this is not as huge of an issue as it appears to be, your own personal car will show you undeniably.:thumbsup: