GDI causing carbon buildup

I have a 2010 VW Tiguan with 48k miles. I recently got the dreaded check engine light and was told that the codes were (P0300 and P0302). The dealer says those are cold start faults caused by misfires on one cyl (so far). They say this is due to carbon buildup on the backs of the intake valves. They further claim that this is due to the fact that the car has Direct Injection which eliminates the possibility of the gas from the injectors cleaning off the valves. They’re claiming that this is NORMAL (expected) at about this mileage for a car with GDI! I’m told this is not a repair issue but simply a maintenance issue which means it’s not covered by any warranty. Can this be true? Will I be expected to shell out $1000 every 48,000 miles for the life of this car??!! Is this happening to all owners of cars with GDI? Do I have any other option other than the 6-hour, thousand-dollar cleaning fix?

Normal condition for the Gasoline Direct Injection (GDI) and Gasoline Turbo Direct Injection (GTDI)… We see this situation all of the time with the Fords. In some cases the build up is bad enough to require an induction cleaning. (Not a big deal).

What the dealer is telling you is true. The GDIs no longer have fuel passing over the intake valves to clean of the deposits from the PCV system, valve guide lubrication and fine particulates within the airstream.

$1000 bucks for a cleaning is a bit insane… 20 Bucks for a can of induction cleaner, a little hands on and done. (I use Motorcraft PM-3)

You can try cleaning the intake valves yourself using a can of Sea Foam.

Here’s how this is done.

  1. Get the engine up to operating temperature and then shut the engine off.

  2. Disconnect the brake booster vacuum hose at the brake booster.

  3. Adapt a hose that will connect to the brake booster hose and into the can of Sea Foam.

  4. With a pair of pliers pinch off this adapted hose.

  5. Have someone start the engine and bring the RPM’s up to 2,000.

  6. Slowly open the pliers so the Sea Foam begins to be drawn into the engine.

  7. Here you will meter the amount of Sea Foam entering the engine by pinching off the hose and opening it to prevent the engine from stalling.

  8. Continue this until all the Sea Foam has been drawn into the engine and then shut the engine off.

  9. Connect the brake booster vacuum hose back onto the brake booster.

  10. After a half hour has passed, restart the engine and bring the RPM’s back up to 2,000.

  11. Keep the RPM’s at 2,000 until the smoke clears from the exhaust.

During this process there will be a lot of smoke coming out of the exhaust. This is normal and nothing to be concerned about.


Consumer Reports had a recent article–titled Better MPG…but at a Price–on this apparently common problem with Direct-Injected engines.

According to CR, several manufacturers–including BMW, Honda, and Kia–have issued TSBs recommending that drivers “use only name-brand detergent gasoline without ethanol, and that they periodically add a fuel-system cleaner”. So…apparently there is a very valid reason to use Top Tier gas, but most of us will have a very hard time finding ethanol-free gas–TSB notwithstanding.

Wouldn’t it be nice if the Iowa/ethanol lobby’s stranglehold on federal gas regulations was loosened? Of course, that would necessitate many federal legislators forgoing the “gifts” that they receive from the Iowa/ethanol lobby, so this will probably not happen.

The article also mentions that one aggrieved VW owner was able to get the approved walnut shell blasting of his valves done for “only” $400 by an indy VW specialist, which was much cheaper than what the guy’s VW dealer wanted to charge.

Additionally, the article mentions that “other” automakers have devised an engineering fix that involves modifying the engine to spray a small amount of fuel directly onto the valves in order to keep them clean. However, CR failed to identify these other manufacturers.

So, there is no question that DI can be problematic. The question ultimately is…What are the manufacturers going to do in order to satisfy customers who have this problem on fairly new cars?


How is any detergent/additive in the gasoline going help in this situation?

Direct Injection means the injectors introduce the gasoline directly into the cylinders. So if the injectors aren’t on the intake manifold where the gasoline see’s the back-side of intake valves, how is that going to help?


Very common problem, heard of it first with Minis.

Find a independent shop.

What about a PCV catch can? (Heck, what about a road draft tube?) If the problem is gunk from the PCV system, it makes sense to make that system clean…or non-existent!

The deposits form on the back-side of the intake valves from the PCV and EGR systems.


Some of those intake valve deposits can also come from residual oil entering past the valve seals due to suction from the intake strokes.

Tester, could you use the PCV vacuum line instead of the power brake line to deliver the Sea-foam or whatever (44K?) into the intake manifold?

If Direct Injection becomes commonplace, I can see another round of motor oil reformulating aimed at reducing or eliminating these deposits…Consumers will not put up with $1000 decarbonizing every 40K miles…

Might be a good time to invest in growing walnut trees and get in on the ground floor. :smile:

When Shell introduced the newest version of their gasoline detergent a few years ago, they stated that they had reformulated their detergents in light of the emerging direct injection technology.

There is an SAE paper on the topic, of detergents and DI engines. Whether it relates to Shell’s formulation or not, I can’t say, but apparently the right detergent can make a difference with DI engines:

This SAE paper applies to deposits inside the injector.

Clearly, the early-adopters of GDI are the beta testers. I think I’ll hold off for a while.

Me too.
I hate to say it, but I see this as another negative and very expensive problem that drivers will be forced to endure because of a regulatory agency’s constant quest for unrealistic MPG levels. It’s analogous to officials in a high jumping contest continually raising the bar until nobody can qualify and then keeping it there until geneticists finally breed a human able to jump it… then raising it again.

I might try a can of this or Seafoam as preventative maintenance on my 2014 Equinox with the 2.4 4cyl with GDI. Doesn’t seem widely available yet. No issues so far at 2 years and 26k miles.

Ed B.

I think that all this talk about carbon fouling of intakes in GDI cars is the PERFECT excuse to justify methanol injection and/or a “wet” nitrous setup! :wink:

“What about a PCV catch can? (Heck, what about a road draft tube?) If the problem is gunk from the PCV system, it makes sense to make that system clean…or non-existent!”

meanjoe75fan, I was right there with your line of thinking about cleaning up the PCV feedback until I read jgree142’s comment that included the valve guide lubrication…dang, I had already made and spent the millions to be gained by developing the disposable PCV Period Pad…A new pad every 30 days…

Perhaps I’ll have to resort to my next invention idea, the Acetone Wet Injection System :wink:

Without forced crankcase ventilation, you will be back to 2500 mile oil changes…The draft tube works but not very well…An open crankcase would be a big step backwards in air quality…Not going to happen…But I could be wrong…Diesel engines somehow deal with crankcase ventilation without any help from intake vacuum…A ventouri in the intake path to create enough vacuum to purge the crankcase ?

Caddyman right, without PCV customers would have to endure very short oil change intervals, internal engine sludging, varnish buildup and component corrosion. All of this would mean shortened engine lifespans, customer dissatisfaction, not to mention environmental issues.

For the light duty diesels (Pickups), as well as more “recent” medium duty trucks, the PCV system is nothing more than one closed/sealed valve cover (On V-type) and the other with a oil/vapor separator with a hose going to the induction tube feeding fresh air to the turbo charger/s. Minimal suction involved, really the flow is created by the blow by gases feeding down from the cylinders into the crankcase. This continuous flow is what drives out the nasty vapors. The turbo inhales the vapors along with the fresh air and crams it into the cylinders for burning. The later model diesels even have flow sensors installed in the PCV systems to ensure ventilation system is working.

The GDI systems have their disadvantages as well as advantages. Disadvantages include the valve build up (again not that hard to deal with), system complexity (High pressure pump/s, high voltage injectors, component access.) they are less tolerant of poor fuel quality, Oil dilution/growth due to gasoline contamination and fairly sooty exhaust emissions.

Look at the advantages of the GDI or really of the GTDI systems. Today’s GTDIs (Gas Turbo Direct Injection) are high compression (10 to 1 or higher) with turbo charging at significant boost pressures. Think back just a decade ago, where turbo charging required reduced compression ratios of 8 to 1 (Reduced engine efficiencies) with high octane (Premium) fuel requirements to work. (At least so it would not ping itself to death) That capability comes from Direct injection being able to cool the cylinder charge down so that the fuel does not preignite. Combine that with the variable cam timing systems, high data rate ignition systems, you get some impressive and clean performance.

Today we have 3.5L V6 engines pushing over 400 emission compliant horsepower, 420 ft. lbs. of torque using standard 87 octane fuel. (And going 7500 miles between oil changes). These things would eat the old smog legal carbureted big blocks for lunch. Ok, ok we can’t perform as many as the old MacGyver “On the side of the road” repairs like we used to. We do however routinely see four cylinders approaching and exceeding 300 hp, all being cleaner than engines we saw in the past and potentially getting 30+ mpg.

All of this is really wild and cool stuff, again it comes with a price. Its more expensive to buy, more things to potentially break, and comes with slightly different maintenance requirements, some of which can be more costly. Then again… no points and condensers to replace regularly, no cap, rotors and plugs to wear out every 30K, no dealing with carburetor chokes or ruptured fuel pump diaphragms, no huge bundles of brittle vacuum lines with ported vacuum switches, no feedback type carbs. They’re just different. I’ll gladly perform an induction service on a GDI before I’d want to spend time trying to get an old Pentastar Lean Burn system working correctly. Just saying.