Why Gas Direct Injection Engines Require Regular Service

Carbon Build Up on Intake Valves

What to do to keep your fuel intake valves from becoming this

Once confined to diesel and high end gas vehicles, direct injection engines have gone mainstream in recent years.  Offering noticeable improvements to fuel efficiency, this high performance system comes with a downside the average driver doesn’t know about: intake valve gunk.

Technically the remnants of oxidized fuel, this build up is easy to manage with regular maintenance.  Unfortunately, most vehicle owners aren’t made aware of the additional needs of their GDI engine – at least, not until they roll into the local service shop with the ‘check engine’ light on. 

How Direct Injection Engines Work

To understand how carbon builds up inside your engine, we first need to understand the process of fuel injection.

In a traditional gas engine, fuel is sprayed from injectors in the intake port to the engine cylinder. During this process, gas washes over your vehicle’s intake valves, clearing off any fuel that has oxidized along the way.

In a modern day GDI engine, the fuel injector lives directly inside the cylinder. This shorter distance allows for a more optimal spray, meaning that less fuel is consumed for combustion (hence your vehicle gets better gas mileage).  On the downside, gas no longer washing over the intake valves, making it very easy for carbon deposits to form.

Why You Don’t Want Dirty Valves

Normal fuel intake valves need to open and close quickly and smoothly. Unfortunately, carbon deposits can interfere with their function, restricting air flow and leading to clogged fuel systems, as well as a host of other problems.

dirty valves engine problems

Signs of intake valve buildup include:

  • Loss of power/acceleration
  • Engine misfires
  • Lower fuel efficiency
  • Engine shaking
  • Jerking/vibration at stops
  • A lit up “check engine” light

Removing Carbon Buildup on Intake Valves

To keep your car’s engine running smoothly, GDI systems should receive a Major Fuel Service every 50,000 km. During this service, your mechanic may remove the intake manifold and clean your valves using a pressurized cleaner.

At Searles, we use a triple cleaning process to clear away build up. First we disable the vehicle fuel pump and tee into the fuel system with a tool that supplies cleaner for the engine to run on – effectively scrubbing away any build up on the fuel injectors. Next, we attach another tool that sprays cleaner into the air intake area of the engine to clean the passages and valves.

Once both cleaners have run through, we install a fuel system cleaner and dryer in the fuel tank.  Post-service, we recommended that owners fill their tank – thereby ensuring the cleaner remains in the system as long as possible.

For a more detailed explanation of the process behind a Major Fuel Service, we recommend this informative video.

Other Methods

In extreme cases of carbon buildup, your mechanic may have to resort to stronger methods to clean your engine.  The below photo shows the intake valves of a 2013 GMC that had gone 62,000 km without a fuel service. Thanks to massive carbon accumulation, our usual cleaners weren’t enough. Instead, we took a more physical route, spraying the valves with a high pressure walnut blast. (Yes, we use actual walnut shells – those things are tough!) As you can see, the difference before and after the blast is night and day.

Carbon Build Up on Intake Valves

It’s important to note that the above process is much more time consuming (and expensive) than your standard fuel service. Prevent a hefty bill (not to mention potential engine problems) by bringing in your vehicle for its fuel service at regular intervals.

What Else You Can Do:

In between Major Fuel Service Appointments, we recommend doing the following to help keep your engine clean and working properly:

  • Go for regular oil changes – we recommend our Best Oil Service for GDI engines
  • Replace older spark plugs (typically good for 50,000 to 80,000 km, depending on the manufacturer
  • Add a fuel system cleaner to maintain the current condition of you fuel system

While these actions will help keep carbon build-up under control,  it’s important to remember that your vehicle still needs a Major Fuel Service every 50,000 km.  If your GDI engine is due for a cleanup, contact us for an appointment. At Searles Auto, we offers this service for $189.95. Rest assured that all of our work is backed by a Peace of Mind Warranty! Book you appointment today!

1 comment

Retired GM tech said:

March 18, 2018 at 6:19 am

Great explanation of just how serious this problem is, even with modern advances such as GDI.

A further preventative measure comes in the form of a “catch can”, located between the crank case and intake manifold.

This simple device will prevent condensation an oily mist from being sucked back into the head, where it will stick to spark plugs, intake valves, pistons in the form of glowing deposits causing detonation under load, producing mystery codes, poor mpg and of course carbon as described.
You might be shocked to see just how much junk is being recirculated, resulting in a mediocre burn at best!

Fitting a catch can is a small investment with big time saving. Research and see for yourself.

Thank you for your time, your engine will too.

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