Cleaning our direct injection GTI’s intake with walnut blasting

Update by Colin Wood to the Volkswagen Golf GTI project car
Apr 8, 2024 | VW, GTI, Mk7 GTI, Walnut Blasting

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The cause of our VW GTI’s rough idle and intermittent check engine light? Our suspicions were confirmed when we opened the hood and removed the intake manifold: The intake vales were covered in gunk–an issue common on many modern VWs and direct injection vehicles.

The solution? Walnut blasting.

Watch the video to learn more about what walnut blasting is, how it works and how successfully the process cleaned our GTI's intake valves.


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MiniDave HalfDork
4/8/24 3:34 p.m.

I DIY'd this on my 2009 MINI at 50K miles, as it was recommended by the dealer......mine were gunked up but it didn't seem to bother it - no rough idle or codes popped up.

I just pulled the intake again at 112K and - clean as a pin! Guess I'll check it again at 160K. It sure needed it at 50K tho......

The walnut shells did a great job, cleaned it up and looked like new when done.

Tom_Spangler (Forum Supporter)
Tom_Spangler (Forum Supporter) GRM+ Memberand UltimaDork
4/8/24 3:43 p.m.

I'd like to have this done to the Expedition. It has a rough idle when cold. Not brave enough to DIY it, and I can't find anyone local that does it.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
4/8/24 3:46 p.m.

Do NOT blast an intake manifold with aluminum oxide material - especially on a turbo engine. Your rings won't outlast your oil change.

Dootz Reader
4/9/24 1:04 a.m.

In reply to Tom_Spangler (Forum Supporter) :

I would start with throttle body cleaning first. Cheaper and easier to rule out first

P3PPY GRM+ Memberand SuperDork
4/9/24 10:52 a.m.

So sweet of the local squirrels to do that for me under the hood of my BMW 

Ranger50 MegaDork
4/9/24 10:55 a.m.

I'm going to fix mine with some wet nitrous...

buzzboy UltraDork
4/9/24 11:02 a.m.

I think understand the root cause of the problem, but why don't we hear about this for direct injection diesels?

Turbine GRM+ Memberand HalfDork
4/9/24 11:50 a.m.

I'm hoping I can put this off until I have everything I need for an MPI retrofit on my Alltrack. It'd be nice to only have to do this once over the life of the car.

xeonoex New Reader
4/9/24 12:41 p.m.

Anyone know how much of a difference having dual injection makes? I have an RS3 which I believe does both direct and port injection. Port injection is supposed to help keep the valves cleaner. I'm not sure what extent though.

I've also heard that running your car hard and getting it hot helps prevent or break down carbon build up, but that definitely seems false now, haha.

alfadriver MegaDork
4/9/24 3:06 p.m.

In reply to xeonoex :

PF-DI should not have the same problem- back in the 80's and 90's, intake system deposits were still a problem, but everyone pleaded with the EPA to force fuel suppliers to have a strong minimum of detergents in them.  

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