By on June 9, 2015

carbon cleaning. Image: Shutterstock user sasha2109

Arley writes:


I have a 2003 Jetta TDI with 178k miles. Runs 100%. My mechanic recommends a carbon cleaning. What are the positives and negatives? To be more succinct, what can go wrong?

You can tune a piano but you can’t tuna fish. (Good to know! – SM)

Sajeev answers:

Conventional wisdom (for both diesel and gas engines) is carbon buildup occurs more often when the owner subjects the engine to excessive idling and a severe lack of full throttle acceleration. Today’s direct injected, EGR equipped diesels (and direct injected gas engines lacking a piggyback port-EFI setup a la Toyota V6s) are sensitive to carbon buildup due to idle time, EGR design and cooling system inadequacies, and perhaps even fuel (i.e. varying quality of bio diesel). Don’t take my word, this company’s blog did a good job assessing the problem.


So carbon cleaning is commonplace and a good idea. And be it a seafoam-alike treatment or physical removal/cleaning of critical parts, there’s no downside if performed with even a modicum of care.

Question is, do YOU have a problem? 

Considering your mileage (less idling and more highway driving?) and engine performance: probably not. Watch this video (go to 1:39) and DIY if you are even the least bit handy. From the video, make a trip to the parts store for vacuum lines too!

Or just do nothing aside from performing an Italian Tune-Up. That’d work for sure, and it’s totally fun.

[Image: Shutterstock user sasha2109]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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21 Comments on “Piston Slap: Oil Burning and Carbon Cleaning?...”

  • avatar

    Heh.. stupid diesel, needs a stent.

    And these crap generators are what Europeans love? Or at least their ministers?

  • avatar

    If you have a direct injection engine you will have to clean carbon deposits at some point. Doesn’t matter what the fuel type is.

    My questions are do the dual injection engines actually address this? If yes, does the doubled injector count and fuel pump pressure regulator add additional maintenance that erases the advantage of avoiding carbon buildup? I’ve only seen anecdotal and theoretical support of dual injection to date, I’m trying not to just assume it’s a net benefit even if it seems to make sense.

    Also it looks like it’s only vag and Toyota using these systems. Toyota in its premium v6’s and the brz/frs 4 cylinder, and vag with its European direct injection engines and some aid is (? In the states? ). Am I right about that?

    • 0 avatar

      The next Ford 3.5EB will have a dual injection system.

    • 0 avatar
      Athos Nobile

      They will probably all have it as it aids with low RPM emissions.

    • 0 avatar
      heavy handle

      Carbon deposits should not be an issue in engines that use valve timing for EGR. I know Fiat’s MultiAir does that, but I wouldn’t be surprised if others did as well (Vanos?).

      • 0 avatar

        I thought the MultiAir had port injection? Also, even if EGR is not used, positive crankcase ventilation could contribute to carbon buildup.

        This is an interesting topic and one that I think has been under-reported in the automotive press. I do have to chuckle at manufacturers’ “buy only top-tier gasoline” edicts. When I looked at the list of brands, I thought to myself, “I wouldn’t know where to buy fuel in my area that’s NOT top-tier” – clearly a red herring from the industry spin doctors.

        I’m curious as to how many miles anyone may be going before requiring a carbon cleaning in a DI engine (gasoline in particular). My close family and friends tend to keep their cars a long time, so only four or five direct-injected cars have entered the collective fleet thus far and none has very many miles yet.

        • 0 avatar
          heavy handle

          MultiAir is DI, or at least the 1.4T version that we get here in various Fiat, Jeep and Dodge products.

          I’ve seen Minis that needed carbon cleaning just out of warranty. It may be a good idea to check the intake valves for buildup every year or so.

          I would imagine that PCV is much less of a worry than EGR. There’s a lot less of it.

          • 0 avatar

            Current mainstream MultiAir engines are port injected.



  • avatar

    As someone who’s owned a couple 2003 TDIs, the carbon cleaning isn’t a big deal, if it is done regularly. There are even vendors out there who will sell cleaned intakes on an exchange basis. The challenge becomes getting the stuff out from the intake ports in the head. Not insurmountable, but you have to be careful not to let the gooey gunk fall in.

  • avatar

    As that mileage, you’re definitely due for a cleaning. As for running 100%, you may think that now, but if you get the intake apart and see a ton of crap in there you’ll probably revise your answer. Anyway, as the former owner of three ALH TDIs which suffered from the carboned up intake problem, you can either pay someone about $300 or more to do it, or do it yourself.

    You need some hex sockets and if you have a kid or someone else with tiny hands to get behind the engine to break the hex bolts loose, all the better! It’s a good 4-5 hour job but it’s also very satisfying when you’re done.

    You have to take the intake off, don’t try to do it with it attached to the engine of you’ll have much more expensive problems down the road. After I removed it, I’d put it on the barbeque on high and just let the oil bake off. Eventually it’ll turn into ash. Once it cools, you can finish cleaning it at a coin wash since they have high pressure water and soap and a grease trap.

    The other method is to soak it in something like Super Clean. I never used that one because I didn’t want to deal with disposing of the gunk that came out.

    Also, do not try and do anything water related to the EGR valve to clean it. Just scrape the crud out and maybe wipe it with a shop towel that has some sort of cleaner on it. I killed an EGR valve by blasting it with water and had to get a new one.

    Once you get it all clean and back on the engine, you’ll probably notice a big difference in the power. In the future, you probably won’t have to do it again. Supposedly since ULSD came into effect, intake clogging isn’t as bad as it was with the LSD that those cars drank up until 2007.

    A good how-to is here

  • avatar
    Silent Ricochet

    A few years back when I bought my car, it had 120,000 miles on it. I invested in a BG Fuel/Air Induction Service, which was done by a trusted local shop for $99. I did a lot of research before deciding to have the service done, and concluded it was worth a shot. Afterwards, I was pleasantly surprised. The engine was much smoother across the entire RPM range, especially at idle. And the engine in my car isn’t really known for smoothness (LD9 Twin Cam).

    Is it worth being done on older, high mileage cars? I think so. Have I done the service since getting it the first time? No. I use a fuel additive every 6 months and I have a bit of a heavy foot so I’m not concerned about carbon anymore.

    • 0 avatar

      I used to wrench professionally and loath BG products. It may have changed, but they used a pyramid marketing scheme involving the parts department and the mechanic, putting their interests ahead of the customers. The product itself is no better than similar ‘induction cleaners’ which are iffy at best- a spray can or two of carb cleaner on a dark night (to hide the billowing smoke clouds) is just as effective. The best way to clean out a dirty intake is to pull it and physically remove the accumulated gunk- a time consuming job to be sure, but scheduled with other services that are easier with the intake off (spark plugs comes to mind) can bring the overall cost down. It’s always good practice to change the oil after injecting any chemicals into the intake (or adding to the fuel tank) to prevent oil contamination problems.

    • 0 avatar

      “I use a fuel additive every 6 months…” — Direct injection bypasses intake valves, so gasoline additives bypass intake valves, as well.

  • avatar

    I had my MDX carbon cleaned out, and it passed pollution and got a few more hp….definitely felt better after 100k. Worth the $175 for whatever they did. The car has been done by the book and then some, so it was up to date and always got

    The diesel TDI has been driven hard since oil change #2. Full temps and rpms are not unusual. I’ve some highways and one or two long uphills in the area. Hoping not, have read too much on BMW forums…I had a mad crush on the 335d but carbon appears to be the tragic flaw. There is much debate as to if US regs cause this. One must assume BMW and VW know how to make a diesel, but MB is on record as saying half of their engineers work on US emission issues.

  • avatar

    When Volvo started selling its first V40 with the T4 engine – a petrol machine – there actually was a Volvo service note recommending an Italian tune up for every service. The instruction was to drive at 5000rpm for so-and-so-many-kilometres in order to reduce internal carbon buildup.

    I can’t fathom how this could be a problem for any car blog reader though.

  • avatar

    One of the first things I did when I bought my W123 was cap off the EGR. Diesels are exempt.

  • avatar

    Engine Carbon is headache for me, but you clear my thought regarding Carbon. thanks for the information. bets of luck for future.

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