Engine air filter - upper filter?

No, it doesn't need to be changed. it is a charcoal 'filter' that absorbs any fuel vapors that may try to escape. This is probably needed since the Atkinson model pushes part of the intake air back out, with fuel already injected into it. The injectors are behind the intake valve outside of the cylinder.

As a side note, it is speculated (mostly by me) that the pushing fueled air back into the intake may be the reason for 'dieseling' we often feel when the engine cuts out at stops.

 

Thank you so much for having this posted. I just noticed that same part number 17812-21020 on the cover today. The charcoal cover makes perfect sense. And also after 4 1/2 years, until today, I thought my 2004 Prius had a slight defect when the engine cuts out at stops, as my 2002 Prius' never did that, including the one I still own. Thanks for the dieseling explanation.

 

Changed the engine air filter on my wife's '08 today for the first time, at approx 10K miles. It seemed a simple task: open hood, pop off the air filter cover, remove the old air filter, install new air filter, re-install air filter cover, close hood, done. Easy enough, eh?

HOWEVER, the air filter's gasket has an rectangular piece along the front edge that sticks out beyond the filter holder and cover. I failed to notice how this "tab" had been positioned on the old filter before I removed it, and it wasn't obvious to me how to properly position it on the new one. I failed to find any discussion (s) about this on PriusChat, after a bit of searching, so some feedback here would be much appreciated.

Donny

 

Hi Donny,

I took a look at my 2004's engine air filter gasket and do not see a tab on the gasket. On my car, the air filter is inserted so that it is closest to the passenger side fender within the air filter housing, and the Toyota part number printed on the air filter is located on the bottom of the filter. The gasket runs all the way around the full extent of the air filter housing's perimeter.

I suggest that you look at the old filter and see which side the dirt is on. That side should be facing down since fresh air enters the air cleaner housing from the bottom (assuming that your car retains the same air cleaner housing design). Then compare to the new filter and position the latter so that it sits in the housing the same way that the old filter did.

If I correctly recall, the Classic air filter may have had a tab on the gasket. That gasket only ran around the paper filter, it did not run around the entire perimeter of the air filter housing. If you happen to have that filter, it is not correct for the 2G model.

 

Donny & Pat,

On my '05 the P/N for the engine air filter is 17801-21040 (the P/N mentioned by a previous poster in this thread was for the filter that was part of the cover---not what we are talk'g about now), & Pat, it does have a thin tab about 1 1/2 inches long protruding about a 1/2 inch off of one of the long sides just a little offset from the midpoint of the long side.

Donny, if you flip your filter over (with the filter material towards the passenger side of your Prius, as Pat said) so that the tab is now toward the rear of your car, you will see that the base of the filter housing has a cutout formed in it to accept the tab. If you still had your old filter handy, then Pat's advice about placing the dirty side down to help determine the original position of the old filter is exactly right.

Another subtle difference of the gasket is that if you lay it down on a flat surface the wrong way, the gasket almost touches the surface all the way around. If you flip it over (to the proper mount'g position), then the gasket is raised off the surface by about 1/2 inch all around except near the end that has no filter material where it droops & touches because of the lack of support. Just keep it in this position now & put it in place with the filter mat'l on the passenger side & the tab to the rear.

Ken (in Bolton,Ct)

 

Ken and Pat,

Thanks for your responses.

Do I ever feel dumb! You were right, Ken, I had the filter in up-side down. Nothing like PriusChat members to set you straight without making fun of you (even though I deserve it).

Donny

 

The whole purpose of the rubber tab is to prevent the air filter from being put in the wrong way. Flipped-over, turned around, whatever, the tab will not go where it belongs.

Even in this case, the tab worked.

The other black filter, mounted in the lid of the airfilter box, is a charcoal filter for absorbing gas fumes from the engine. (Evaporative emission control, like has been on gas tanks for decades) Those new filters have been on most all Toyota since 2004-2005. Alot of truck owners will remove them to enhance intake/engine performance. They can be removed by simply drilling out the little columns that support it in the lid.