Replacing The Stock Air Filter Unit

By Andy Woo

Created : 971002
Last updated: 981109

So that if I ever have to do it again, I have recorded what I did in order to replace my stock air intake unit, with an after market air intake unit. I have successfully done this twice to both my Z's.

Suggested tools :
10mm socket with socket extension
10mm box-end wrench
8mm wrench (could have used 8mm socket)
philips screwdriver with fairly large head

Here is my car. I open the hood to get access at the screws necessary to remove the center piece. This is the piece between the two headlights.

Car with engine hood up


Here is a better shot of the center piece. Notice the four screws that I have to remove. Two on the left side, and two on the right side.

four screws to remove front piece


As an example, here is a closer look at the two screws I'll have to remove on the right hand side of the center piece.

close up of left two screws


This is what is underneath the center piece. The stock airbox. Notice the big rubber hose running from left to right in the picture? This is a "T" shaped hose, with a square box attached at the bottom of the "T". This square box is the air flow meter. Be very careful when handling this piece. And below this combination is the black plastic air intake unit.

picture of air box and hoses


To unmount the air intake unit, there are a number of steps I must do. First, there are four screws that mount the air intake to the chassis of the car. Two on each side of the air intake unit. One on either side that is very easy to get to. See it? It's mounted onto chassis readily exposed. Here's a picture of it on the left side.

one of four screws to dismount airbox


And then there are two that are really a 'pain' to get to. They are screwed in deeper towards the bottom part of the air intake unit. It's tough to point out. Whereas the screw for the top part of the air intake, is both above and exposed, and to the top left (and top right), this screw is 'below' and hidden, but is of the same size. I found using a stunted philips screwdriver, or using a piece from my rachet set, with a short extension only attached to the piece.... to be the two easiest ways to get them off. If easy is something one can call it. I had to be patient on this one... I don't want to be dropping my screw drivers in my car. If it is too painful, you can wait until step 14 (when you've removed the top of the air filter box, and removed the air filters themselves) then try again when you have a little more room.

one of four screws to dismount airbox


So, here we are at the air flow meter box.

air mass sensor


On the right hand side of the air flow meter, is a connector for wires connecting into the meter. This must be removed. Before I yank at it... I must remove a small, slim, rectangular shaped metal 'ring'. This helps prevent the connector from accidentally disconnecting itself during 'spirited driving' . Be very careful when removing this 'ring', as it's almost 'spring loaded' the way it comes off. I would suggest keeping my hand completely wrapped around the metal ring, and then carefully and slowly, use a thin screwdriver to push/pry one open end (oh yeah... the metal is open ended. It forms a rectangle, but with maybe a half inch of the top part of the rectangle missing. I'll see what I mean when I see the unit up close) of the ring away from the connector. As I do this, get ready to grab hold of it with the hand that is completely covering the connector (remember?). I should then be able to 'un-wrap' the ring. Phew... I don't want to drop this ring... I'd have a tough time recovering it from somewhere in my car .

air mass airflow sensor connector


On the air intake unit, there are four clips that hold the air intake unit cover onto the base unit. They are in each corner of the air intake unit. Here's one of them at the top right hand side. I should now proceed to unclip these. Also notice the missing screw from the air intake unit mount? Remember? I removed these at the beginning of this process.

clip to remove top of stock air box


Ok... now, where's the air flow meter again? Oh yeah... here it is. On the left hand side and where the air flow meter joins with the air intake hose, there's a clamp holding these two pieces together. I want to loosen this screw up. Because when I remove the air intake unit, I will be removing the air flow meter still attached to it as well. I don't have to remove this screw... but keep it pretty loose.

screw to clamp that connects mass airflow sensor with 'T' hose


Ok... now I'll remove two screws that also hold down the cover of the air intake unit onto the base unit. There is one on either side of the air flow meter. See it?

one of two screws holding top of airbox


Ok... there is yet another screw... this one is a long screw. This is mounted close to the bottom (meaning near the bumper) between the air intake unit, and the bumper. This is a long screw, and I just have to loosen it enough so that I can pull it out. I think there is a slip nut in there, so that I can't pull it completely out of the air intake unit. At least not easily. Doesn't matter.. I don't have to remove the screw.

long screw holding front part of stock air box


If I now remove the cover of the air intake unit, I will see two red air filters.

cover of stock air box off exposing stock paper air filters


Remove them and this is what I should see. Now.. I also see a 'splash guard' below the air intake unit. This is to prevent water from splashing up. There are two screws that mount it to air intake. When I remove the screws... the splash guard will still be attached to the car towards the bumper side, but towards the dash side, it will just droop.

air filters removed exposing inside of stock airbox


Ok, there are two hose clamps on either end of the 'T' air hose that I have to loosen. I'll have to loosen it because as I remove the air intake, the 'T' air hose, will naturally want to twist with the air intake. Instead of twisting the hose, if I loosen the hose clamps, there'll be less resistance. Ok... once I've done this... and hopefully I've been doing my chest exercises ... I'll now be trying to remove the air intake unit. I should only be left with the bottom part of the air intake unit still attached to the air flow meter. I should have removed the cover and the air filters. Ok... the trick here is grab the air intake unit from both sides... and as I squeeze it together, pull the air intake unit up out of the car. This is by far the TOUGHEST part of removing the air intake unit. Be patient... many others including myself swore a lot during this step of the removal. Resist the temptation to take a hack saw to dismember this beast ! .

one of two screws holding clamp around 'T' hose


Congratulations... I've past the worst of it. As I can see, here is a picture of the air flow meter unit facing up at I. It's still attached to the air intake unit. Remove the four bolts on the air flow meter so that I can separate the meter from the box unit. Be careful not to lose the little gasket/washer that is currently sitting between the air flow meter and the air intake. The air flow meter's got a nice little groove for it to sit in. But it sits there without any glue, or anything.

four screws holding mass airflow sensor to stock airbox


Ok... now mount the air flow meter onto my new air intake unit. Don't forget the gasket/washer between the air flow meter and the new air intake unit. I'll now have plenty of room to install the new air flow meter/air intake unit back into the 'T' intake hose. Turn the air intake combination downwards a little so that it's angled down. Then re-tighten the hose clamps on either end of the 'T' hose, and re-tighten the screw for the clamp connecting the air flow meter with the 'T' hose.

new air filter unit reconnected and re-installed


If I have the air intake unit that has a bolt at the top of it (the end that is now pointing downwards), I now should push that bolt through (yes, as in piercing) the splash guard, and bolt the air intake unit onto the splash guard. This will help prevent the splash guard from bouncing around.

bolt at top of air horn bolted onto water splash shield


Last step... re-connect the connector to the air flow meter, and re-mount the rectagular shaped metal ring. Re-tighten everything that had been previously loosened (hopefully, I remembered to mention all the re-tightening steps... but just in case). And then re-install the center piece.

re-connect and re-clip mass airflow sensor connector


Phew.... well... that's how I went about changing my stock air intake box unit, with the aftermarket air intake unit.

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