How To Walnut Blast Intake Valves on BMW 335i! (DIY)

Walnut blasting is the procedure that removes carbon buildup on the intake valves. Unlike most cars, the 135i, 335i, 535i and 550i have direct injection instead of port injection. This means the fuel injectors spray directly into the cylinder instead of through the intake ports on the head.

Port injection constantly washes the intake valves with fuel, keeping them clean. However, direct injection bypasses the intake valves so they have nothing to keep them clean. Hence the need for this manual carbon cleaning procedure.

My 2009 BMW 335i (N54) finally got the walnut blast it deserved at 140k miles. After purchasing the car and talking to the previous owner, I became aware that the valve cleaning procedure had never been performed.

The walnut blasting service is recommended at 75k miles for the N54, and then again every 50k miles after. So this car should’ve had the intake valves cleaned twice already! Oh well, better late than never, right?!

Since it had never been done, I was getting a rough idle and a grumpy cold start. Cleaning the carbon buildup off of the valves would allow for better air intake.

This isn’t my first time walnut blasting an N54, as I’ve done it to my 135i twice before. I pulled the car in and got all of my tools and materials ready.

Here are the supplies I used:

• Fine Grade Walnut Shells
• Intake Valve Cleaner
• Intake Manifold Gaskets (6)
• Abrasive Blaster Kit
• Vacuum Adapter & Blasting Wand
• Brass Adapter Fitting
• Remote Starter Switch
• Pick Set
• 8mm, 10mm, 11mm, T20, T25 & Hex Sockets
• Pistol Grip Blow Gun
• Shop Towels
• Vacuum
• Air Compressor

Intake Manifold Disassembly

Here are the steps I took to get to the valves…

• Cowl and cabin air filter removal
• Air box removal
• Charge pipe removal
• Intake manifold removal

Walnut Blast Procedure

Well, I think I figured out why the car couldn’t eclipse 13’s in the 1/4 mile! I couldn’t believe what I found after removing the intake manifold!

After loosening up some of the carbon with a pick…

Then after one pass of walnut blasting…
(see video at the top for a detailed explanation of how to do this part)

Lots of walnuts and manual scrubbing later…

I even cleaned up the intake manifold ports because those were caked with carbon as well. You can see the cleaned port on the left and the dirty port on the right.

It was a lot of work, but totally necessary. If you want to watch my whole process with more of a DIY/How-To style, check out my YouTube video. It also has some more information and a drive at the end showing the power increase/restoration.

Performance Improvement

I was able to restore performance and shave 0.41 seconds off of the 0-60 time by doing this walnut blast. No other variables changed and the launch was identical (as you can see by the 0-10 time).

I hope this helps other N54 enthusiasts!

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