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I have a tech question concerning the new direct injected engines from GM and I figure you all hear are more knowledgeable than some sedan forum.
I also want to ask here to see if we are going to see the same issue on my dads GMC All Terrain with the 6.2L direct injected motor
I have a 2013 Chevrolet Impala 3.6L direct injected motor with 100,000 miles that hasn't had one hiccup.
I recently pulled the intake so I could change spark plugs and coil boots.
I noticed carbon building up on top of the intake valves.
I won't say it's a lot but more than I would like to see.
I am learning this is common with DI engines as you don't have the fuel spray constantly washing the valves clean and the build up is from fumes or vapors pulled from the engine by PCV system.
I also cleaned the throttle body as it was pretty dirty/oily inside.
I also had oil in the intake boot from the air filter housing to the throttle body.
You direct injected V8 guys seeing the same things?
Anything we can do to prevent this?
My 2011 Infiniti M56S was terrible at 90K. I ended up using crushed walnut shells to media blast the valves after using B12 to soak the carbon to loosen it up. Worked really well although a bit messy. I went from having P0300 random misfires to a healthy V8. Power and Fuel Mileage both increased. I am using GM Top Engine clean every 7,500 miles now prior to every other oil change. The valves in some cylinders where so gummed up with oily carbon they were leaking compression back into the intake causing the misfiring at lower rpm under load.
yup, no real way to avoid it.... catch can on the pcv may help some, water/meth system on my other car helps, walnut blasting every 50k miles isnt that bad
I would absolutely be running a catch can on the dirty side and a check valve on the fresh air inlet to the intake tube. B12 chemtool cleaner is the best cleaner I've found. I prefer it in the spray can, so hold out for that if you can. Otherwise it comes in a pour bottle.
I am a tech at a Ford dealership. Almost all the new vehicles are DI. The carbon build up is a big problem we see all the time. Ive seen some valves look like the ones pictured above on cars and trucks with 20-30k miles. No way around it. From what ive read on the Ford tech websites newer vehicles are going to come with DI, but are also going to have a second set of injectors to spray the valves to help with the carbon build up problem. Don't judge me being a Ford tech I am die hard chevy. I have a Silverado and a Tahoe and my wife has a Tahoe. This was the first place I got hired at out of school and 12 years later im still here. Fords Suck!! trust me I work on them.
As a mechanic, it pays to work on less dependable cars. I knew a Land Rover tech who was making near $200k at a dealer because he was a MACHINE and would also constantly have an underling in training multiplying his efforts.
I installed a catch can system on my truck the day I got it home.
Used the UPR dual valve setup.
Hoping it works enough I dont have to do a major cleaning anytime soon
10-19-2017, 09:44 PM
Direct inject and carbon build up
