5th Gen Mods, Install, Maintenance

4Runner Air Pump Mod

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Secondary Air Pump Mod on 5th Gen 4Runner

Air Injection Pump Preventative Maintenance, Uni Filter – Air Pump Filter Swap

This modification has been done widely in the Tacoma and Lexus GX460 area where the foam element inside of the secondary air intake pump can break down over time, and eventually lead to a pump failure if the foam element is introduced to the propellers of the pump.

While some say that they have checked the foam element within the pump housing after several hundreds of miles if not more and have found it to be in serviceable shape, I decided to do what many other Tacoma and GX460 owners have done and replaced the foam element in favor of a Uni Filter UP-107 1” clamp-on breather.

The filter can be found on Amazon at the link above at the time of this article for around $14. As the pump only runs on startup and when the motor is turned off the filter will be unlikely to need attention on a regular basis, however, the Uni Filter is a washable filter that can be oiled if needed similar to that of K&N filters.

Tools needed:

Locate the Air Injection Pump

The air intake pump can be found on the passenger side of the engine compartment next to the air filter housing and the windshield wiper fluid reservoir.

Remove plastic cover on the pump

The plastic cover has a tab facing the front of the vehicle that needs to be pulled up on and then you can use your other hand on the side facing the air filter house to pull on that side of the cover while lifting up. It is a tight fit and does require a bit of force to remove so don’t worry if it feels like it might break.

Remove center T25 Torx screw

With the cover off you’ll be able to take off the T25 Torx screw in the middle of the air pump housing that is holding the cover down on the element. Once the T25 Torx screw is removed you’ll be able to lift up on the air pump housing cover and the foam element along with the propeller blades will be exposed.

Remove the foam and the air pump cap

You’ll want to take out the foam element from the housing and also take off the cap on the end of the air pump housing that you just removed. This is the part where you will take a flat blade screwdriver (or another prying tool of choice) and pull up on the tabs attached to the cap. There is a small lip on the end of the air pump housing that the cap needs to have the tabs pulled over in order to be removed.

Install the Uni Filter

Once the cap is off you can slide the Uni Filter onto the air pump housing inlet. It is a snug fit so you can push on the end of the Uni Filter using a rag to seat it all the way down the inlet. Once it is on the inlet, proceed to tighten the clamp down. The fit is snug already so the clamp doesn’t need to be torqued down, a few turns will be sufficient for this part.

Replace the air pump housing

Go back to the engine bay and replace the air pump housing back on with the T25 Torx screw. This is another screw that needs to be snug rather than torqued on possibly cracking the housing. There is also a plastic ridge on the housing that will seat with the cover when putting it back together as shown in the photos.

Replace the Air Injection Pump cover

Replace the first plastic cover that was over the air pump housing by pressing it into place and verifying that the tab snapped back into place facing the front of the vehicle. This completes the modification for the air pump and the chance of the foam element degrading and causing a failure of the pump!

Save housing cap and foam if needed

I’ve also decided to keep both the foam element and housing cap in case I need it for emissions or any other purposes. I placed them in a labeled zip lock bag after the install was completed for safe keeping.

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Hi John, thanks for the article! I had this done but didn’t remove the foam insert. Do you think I should? I didn’t think the K&N filter would obstruct the airflow much and thought double the protection the better.

Bryson Hicks
Bryson Hicks

Got a link to the filter? Unless I’m blind, I’m not seeing one.


Same, don’t see a link


Install was pretty easy after following your instructions and even passed my 5K inspection (kind of useless) but wanted to say thanks for the great write up’s and flatter wallet 🙂

Bryson Hicks
Bryson Hicks

The housing cap actually fits perfectly over the filter. I put it back on to give the filter some protection from dirt.


Thanks for the write up John, well done. Can someone explain the purpose of this Air Injection Pump? Is it simply to reduce emissions after startup? Merci.

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