Next in my series of DIYs of stuff that should be obvious but isn't: engine air filter replacement. Getting to the airbox involves removing the air intake and unclamping a few hoses. There is a howto on audiworld.com, but to be honest I found it confusing and there were no pics. So in the end I used a different procedure and snapped a few pics while I was at it.

It'll take you 30-45 minutes to do, which includes reading this DIY.

What you need:
  • New air filter - you could go K&N if you want. People disagree about whether it's worth it. Do a search.
  • Phillips and flat-head screwdriver
  • Needle-nose pliers
  • A small hose clamp (I think mine was 15 mm?)


Procedure:
1) Open the hood. The air intake is to your left and has two pieces that clip together in the middle. To remove the front part, remove the two screws along the front edge and the pull the first part backwards. Be firm but gentle, so you don't break any of the tabs that hold the two bits together. Finally, remove the rear portion by pulling upward, noting the little tab (circled) that holds it in place.


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Careful as you pull the rear portion out of place: there's a lot of dirt in there that you'll want to remove with a shop vac. Also note the little snow screen that's located right at the end of the rear portion of the intake where it connects to the airbox. Mine was filthy, so I rinsed it in water and brushed off the dirt. I bet I gained a full 2 hp from all the crud I cleaned out of there

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2) There are 2 screws at the top of the airbox. Unscrew them:


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3) It helps to unclip the sensor that sits at the top of the airbox, which you do by lifting the little tab with a flathead screwdriver


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4) Right behind that sensor is a hose clamp, which you have to remove. Audi uses a single-use clamp that is a bit of a pain to remove. I like to stick a set of needle-nose pliers in the gap and twist, and then peel the clamp away. Here's what it looks like after I removed it, and pulled the hose away from the valve:

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Note for reinstall, I used a regular hose clamp.

5) There's a wire harness running along the edge of the airbox that's help in place with three clips. The clips pull away fairly easily using a large flathead screwdriver for leverage. Just don't break those wires, they're probably important or something. Here are the first two, located just below the screws you just loosened:

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And here's the last one, tucked away near the back:


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6) If you did it right, you should now be able to push the airbox lid open enough to yank out the old filter. Just push it firmly but carefully toward the engine:

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Appreciate how dirty your filter was, because, like me, you couldn't figure out how to do this till now (and were too cheap to pay the dealership to do it now that you're out of warranty):


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There was a lot of crud down there in the airbox, so I carefully cleaned it out with a shop-vac.

7) Install new filter. You do remember which way it went in, right? Be careful you don't rip it as you slide it in place, and make sure it's seated correctly before shutting the airbox lid:


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8) Put everything back into place - it's just the reverse of the install. Remember to re-connect that sensor wire, and to clamp the vacuum hose back into place!