Carbon Buildup and Direct Injection

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Thread: Carbon Buildup and Direct Injection

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    Carbon Buildup and Direct Injection

    Today's Tribune (auto section; Motormouth) has a question/answer regarding carbon buildup in direct injection motors. "Will fuel additives also benefit newer direct injection systems?" The answer was added as "Yes, up to a point. While the additives will do nothing to remove carbon buildup on intake valves, they may help to keep the fuel injectors clean. Dirty valves are a growing problem that leads to rough idle and cold-start hesitation. Although there is some speculation as to the cause and possible control of carbon buildup on direct injection engines, we have seen nothing convincing yet."
    Which led to think that DI is really new to production vehicles which points to a greater rate of buildup when compared to non-DI engines. When rebuilding the 3L on my 89 Caravan (175,000 miles), I inspected the valves and found them to be almost spotless. I would think that this sudden recognition of buildup points to a new problem that DI has introduced. Are we getting a 1-2 mpg increase but sacrificing performance and reliability in turn? I did not know of this supposed problem until reading the paper.

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    Re: Carbon Buildup and Direct Injection

    I think this was an issue that was simply not foreseen when the engines were designed. My guess is that in the mindset of the designers, the "clean" intake charge would prevent carbon buildup. I guess they "forgot" to take into account crankcase and EGR gasses.
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    Re: Carbon Buildup and Direct Injection

    It is a recognized problem with DI engines. The EGR system puts fumes and deposits on the pre-combustion intake valve surface, and since the fuel from a DI engine is injected, the cleansing from gasoline doesn't happen in many cases. Toyota apparently uses a combination of port and DI, which should eliminate the problem. GM has a patent-pending system on the new V6/8 Gen V engines that may prevent the build-up.
    To me, this is a major problem that needs to be solved, and is especially bad on German cars.
    This also points to the current engines, like the Gen IV V8s, as being a good choice until the problems are solved.

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    Re: Carbon Buildup and Direct Injection

    I must ask how bad the problem is. How badly is performance being affected? The average owner will know nothing until a problem appears regarding driveability and fuel consumption- things that the owner will notice. I was thinking of purchasing a new Grand Caravan but my 98 GC (3.8L and 90,000 miles) and my 2004 supercharged Monte (although only 20,000 miles) have given me no problems. After reading the story and your input (Gotta luv that German cars are especially affected. Funny that it is not advertised as if they were domestic), I think that I'll wait a little longer.
    It also sounds like the chemistry of the fuel will need to be changed to combat the problem.

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    Re: Carbon Buildup and Direct Injection

    VW and Audi in particular have been singled out with the problems, but a better approach would be to learn where and how the fuel gets to the combustion chamber. If you don't prevent the EGR gases from building up on the intake valves, you are looking at a tear-down and high expenses.
    I don't know how large the problem is, but it is worth watching.
    I suspect that as long as EGR gases are introduced, there is the potential of problems. Toyota's approach of port injection AND DI may be the answer, but I'm not an engineer, so maybe an engine engineer could weigh in.....

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    Re: Carbon Buildup and Direct Injection

    My shop, like most others, offers a fuel injector "cleaning" that is added to the tank, and through an intake vacuum hose prior to the intake valves.

    Im gonna try it soon with my Equinox 3.0L and report back.


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    Re: Carbon Buildup and Direct Injection

    See Direct Injection Carbon Issues? 5/20/13

    Yes, "new problems" to understand and solve.

    Question: How does US and EU experience differ? IF different ... what causes the difference. Note that the EU has been using DI diesels for what ... 40 years or more? There should be a history.

    Possible origins?

    - crank case emission control systems, i.e., PCV system (including lack of some kind of "vapor trap")
    - engine lubricant characteristic (and residues)
    - fuel characteristics (and combustion residues ... returned through EGR)
    - maybe even valve operating temperature (design)?

    How is that for a few places to start?
    It is important what WE use as our "moral compass" and ...
    the "measuring stick" chosen for judging progress/success as well.


    44 mpg by 2010 ... 2013?

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    Re: Carbon Buildup and Direct Injection

    Quote Originally Posted by mrDenali View Post
    My shop, like most others, offers a fuel injector "cleaning" that is added to the tank, and through an intake vacuum hose prior to the intake valves.

    Im gonna try it soon with my Equinox 3.0L and report back.


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    This sounds like a very simple and logical solution.

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    Re: Carbon Buildup and Direct Injection

    Quote Originally Posted by 44 mpg by 2010 View Post
    See Direct Injection Carbon Issues? 5/20/13

    Yes, "new problems" to understand and solve.

    Question: How does US and EU experience differ? IF different ... what causes the difference. Note that the EU has been using DI diesels for what ... 40 years or more? There should be a history.

    Possible origins?

    - crank case emission control systems, i.e., PCV system (including lack of some kind of "vapor trap")
    - engine lubricant characteristic (and residues)
    - fuel characteristics (and combustion residues ... returned through EGR)
    - maybe even valve operating temperature (design)?

    How is that for a few places to start?
    Thanks for referencing the other thread. I was just about to...

    I've also read that ROAD TRIP! ROAD TRIP! where the engine gets up to proper op temp and runs for a few hours will help in cooking off any buildups.

    I know that Way Back When, when we'd take a multi-day trip in the family saloon, MPG on the second day was better than Day #1, also because (presumably) some junk had gotten burned out of the system.

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    Re: Carbon Buildup and Direct Injection

    Quote Originally Posted by VMax2007 View Post
    This sounds like a very simple and logical solution.
    It does. I always thought it was poppycock till I figured its benefits on my car.


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    Re: Carbon Buildup and Direct Injection

    Apparently, there is no simple answer to cover all applications.

    It would seem that everyone can benefit from clean injectors. If your normal gas purchase includes fuels that have the minimum legal additive, you're going to get dirty injectors before anyone else. If you have an engine setup that is prone to valve buildup (the aforementioned plus some BMW's ect) you're going to hasten the problem with minimum additive fuels.

    Be aware that auto manufacturer's warranty's do not cover drivability or engine failures due to problems resulting from low quality fuels. That would be between you and your fuel distributor. Whether or not the problem is a design flaw in an engine prone to carbon buildup is probably a sticky situation that most reputable attorneys will either not touch with a ten foot pole, or you as a non-multi-millionaire with neither an inexhaustible bank account and time/patience don't want to go there. So as one who has the good sense to frequent forums like this one, ask questions about the vehicle you're going to buy. If it does tend toward carbon build up problems, and you just have to have it, protect yourself and run high quality top-tier fuels.

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    Re: Carbon Buildup and Direct Injection

    This has also been an issue with the Ecoboost, among other things. High quality fuels do NOT fix this problem, I think it was Lexus that has a second injector acting as a "cleanup" injector to help this problem.

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    Re: Carbon Buildup and Direct Injection

    The GDI Deposit issue is a real problem.

    Cause is multi layered.
    1. No fuel wash from injection system.
    2. PCV vapors coat the valve/stem/port
    3. EGR particulates add to the issue.
    4. Mileage and extended oil change intervals cause compression ring land deposit that sticks rings to the piston increasing blow-by, increasing PCV vapors, increasing valve deposit.
    5. The other problem is the deposits in the combustion chamber and injector tip. The injector has a director plate on it, creating multiple spray streams targeting the piston top. The piston top has a very specific shape so when the high pressure fuel streams enter the combustion chamber the shape of the piston will properly distribute the fuel through out the combustion chamber. When the deposit build up covers the injector tip, effecting the director spray pattern, and changes the shape of the top of the piston, the engine is less efficient and less powerful. This condition can be mitigated with the use high quality furl tank additives such as BG's 44K.


    90% of the issue is caused by oil vapors from PCV induction. This vapor coats the valve in layers of deposit every time the engine is shut down. These layers build over time and mileage. The light distillates evaporate, leaving the heavier deposits. GDI combustion chamber temperatures are much higher, due to "stratified lean mode" of air fuel mixture, 30:1 to 50:1 Air fuel ratios. The higher temps create a much harder valve deposit, that does not respond well to vaporized induction procedures. Also vaporized induction cleaning is ineffective on variable intake systems.

    Here is a test of a GDI vehicle from new to over 60,000 miles. BG Fuel Test. The test was performed on a Ford Taurus SHO TT V6, bought new to run this test. Factory scheduled maintenance was followed till 32,000 miles. The results speak for themselves. The test includes regular oil and fuel analysis, boro-scope pictures and videos, dynamometer testing, and seat of the pants commentary. All of this information is included on the website.



    GM Recognizes the issue:
    PIP5029C: Engine Misfires Due To Major Carbon Deposits On The Intake And Or Exhaust Valves - (Apr 23, 2013)
    But the procedure does not work effectively, you may have to perform this x5 or so and the valves are still not clean.

    Look at the second picture in the PI. Notice the mushroom cap of deposit on the valve stems? Do you see the fractured and missing deposit on the valve on the left side of the picture? The fractured deposit can set P0300 P030X DTC's as it passes through the induction system. Possibly, Holding the intake valve open, closing the gap on the spark plug, or holding the exhaust valve open. Customers complaint is MIL or rough running that may have cleared by the time it arrived at the dealership. Cylinder specific or generic P030?, but no indication of a current issue. Until you pull the upper intake plenum and see the fractured valve deposit. I have seen quite a lot of this on 3.6's and some on the 2.4 SIDI.

    Toyota/Lexus has issued a bulletin that instructs the dealer to install stronger valve springs to crush the deposit fracture.

    Ford and VW/Audi are also experiencing major issues, BMW as well.



    Direct Injection Carbon Issues?
    Last edited by Jim Injun Ear; 06-02-2013 at 09:49 PM.

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    Re: Carbon Buildup and Direct Injection

    Quote Originally Posted by Pinnacle View Post
    This has also been an issue with the Ecoboost, among other things. High quality fuels do NOT fix this problem, I think it was Lexus that has a second injector acting as a "cleanup" injector to help this problem.
    this is a way to get the cleaning of the intake valves without opening up the engine head and scraping the junk off.
    It may be that Toyota is the only company doing it right, although GM's new Ecotec3 engines have a new patented system designed to minimize deposits.

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    Re: Carbon Buildup and Direct Injection

    The "...unintended consequences..." of "...progress for progress's sake..." and EPA's mandated MPG requirements.

    Engineers have known for decades the "washing" effects of gasoline and detergents in fuel in normally aspirated engines--especially aircraft engines, which were among the first piston gasoline engines to attempt using direct gasoline injection.

    They--(GM et. al.)--took a gamble...and, although they haven't LOST (yet), they sure as Hades have NOT WON (yet) either!
    Last edited by 70AARCUDA; 11-21-2013 at 05:59 PM.
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