How Do I Tell if I Have Carbon Build Up in my Engine?

If you are not sure what carbon build up is then you should go read this article first.  It is a big issue on the directed engines that are so prevalent now, and cleaning of this carbon needs to be considered as part of your normal vehicle maintenance routine.

The advantages of a carbon clean, which is typically done as a walnut shell media blast cleaning, are well worth the cost.  You will see:

  • Improved fuel economy
  • Improved throttle response
  • Smoother idle
  • Improved power

Now, the big question of how do you determine if you are in need of this service?

Mileage – Typically if your vehicle has tipped past 60,000-75,000 miles on the odometer you could reap the benefits of a walnut shell blasting service.  This is a lot of tanks of fuel and engine revolutions that just bit by bit carbon is building up on the back side of those valves.

Rough Cold-Start Idle – If you notice that your vehicle is not quite as smooth, and rough in the morning you may have a carbon issue.  As the carbon builds up on the valve it disturbs the air flow as it was originally engineered.  When the vehicle is cold the carbon is more rigid and this causes a more pronounced air flow disruption.  As the car heats up the carbon becomes more pliable and the disruption becomes less pronounced.

Reduction of Fuel Economy – If you pay attention to your fuel economy and notice that it starts declining, you may have a carbon build up problem.  The carbon build up on the valves causes a less than efficient fuel combustion operating condition resulting in a loss of fuel economy.  A walnut shell blast will restore this fuel economy.

Loss of Power – If you notice a loss of high RPM power or hesitation off the line, then you may have a carbon problem.  Just like with the loss of fuel economy the carbon build up reduces the efficiency of the engine.  An inefficient engine not only uses more fuel, but it also produces less power.  A good cleaning of your valves will restore this lost power and put a smile back on your face when you push down that right foot. 

Check Engine Light – When then carbon gets severe enough it will actually induce a misfire that will cause a check engine light.  If your vehicle has reached this point you have likely ignored all of the prior early warning signs.  If you are at this point then you should run, not walk to your local service center to get some vehicle maintenance.

So, if you are to this point and still just have to know if you have a carbon problem on many vehicles this is something that can be inspected.  What you will need to do is gain access to the intake valves.  The easiest way is to pull a pressure sensor to gain access.  This can be seen in the image below. 

VW MK6 GTI intake manifold pointing out boost pressure to inspect carbon build up with bore scope

What you will then need to do is pull the sensor and use a borescope to get a view of the valve.  If you see something like this image, then you need a carbon clean.

Carbon build up on a MK6 VW GTI valve using a borescope

If you own a vehicle that is direct injected, carbon build up is a fact of life.  A walnut shell blasting should be considered a normal maintenance repair for your BMW, Volkswagen, or any of your other European vehicles.  We would be more than happy to help you with this service as we have successfully cleaned countless valves. Your valves should look like the picture on the right, not those black nasty globs in the other pictures.

Intake valve before and after walnut shell blasting showing all of the carbon deposits removed

As soon as you notice any of these symptoms give Alex’s Autohaus a call at (801) 566-6115 and we would love to help you with your BMW repair and Audi repair services.

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