I noticed immediately after doing the deckplate modification that my truck was slower at wide open throttle (wot) than it was at 3/4 throttle. I cleaned the MAF and scanned the ECU for engine codes to no avail. A few days ago I replaced the stock airfilter with a TrueFlow airfilter and these symptoms completely went away. Rather than slowing down at WOT, it now develops noticeably more power than ever. So the question is, why would this happen? Obviously the stock air filter is more restrictive, but the MAF should have detected a lower airflow rate and adjusted accordingly. I have a pretty strong understanding of the air metering system and the effects it has on engine control, but this one has me baffled. Any ideas?

 

I had a similar situation when I did my deckplate. (6") I only had the stock filter afterward in for two days when I received my TRD filter (K&N) and I noticed an immediate difference off the line as well as at WOT. I assumed it simply had to do with the difference in air flow.

 

The 3.4 engine is well known for being starved for air on the 4Runners - it's that dern elbow in the airbox. I'm not sure if the Tacoma's have the same issue, they may.

anyway.. When you open up the front of the airbox, but leave the stock filter, it's possible that you created a vortex in the box right in front of the filter. That would explain the dogging up top - you go to WOT, the ECU goes to open loop, there's no air to match the fuel, and you're running rich.

The vortex may get to the point that you simply can't get air... With the elbow still in, it would act like a baffle or limiter and you'd still be able to pull air into the engine - though not as much as you could have.


Past all that... Enjoy the deckplate!

 

I have a similar theory. It's either related to pressure in front of the filter or some type of vortex; it certainly is not related to a change in airflow through the filter (the MAF and ECU would adjust automatically for those types of changes).

If you're still using a stock airfilter with the deckplate, time to upgrade!

 

And this, Masters, is why I am yet the Padawan...

I never thought of the difference in air pressure, although it certainly makes sense now.

 

I don't know, I hear a new paper filter flows just as well (if not better) than drop-in filters such as K&N and Amsoil. I just have to find that chart...

 

That is only true when they are brand new.

Did people reset the ECU (pull the negative terminal) when they did the mod?
I have seen cases where just pulling the ECU fuse did not completely clear the computer.
Wihtout clearing the ECU properly it may be sluggish while it relearns.

 

I reset the ECU. I put about 3,000 miles on it with the paper filter and the situation never improved.

 

FYI the tacoma does not have the elbow in the airbox. K&Ns have a bad habit of letting dirt in after the filter gets clogged because it relies on that purple fluid to catch particles. That purple stuff also has a tendency to coat your MAF sensor which results in a CEL.

 

My 98 Tacoma LTD 5VZFE had the elbow. In fact, I still have the one I pulled out in my garage (even after I sold it long ago). I agree about the K&N part.

 

I like the TrueFlow airfilter so far. I would like to see some published results for airflow and filtration ability compared to the Amsoil.

 

Check out the Gadget site. It has more than you ever knew you never wanted to know...
Anyway is has lot of info.

 

My '99 HAD it until I removed it and added a 4" deckplate.

 

I couldn't find anything on his site related to the TrueFlow airfilter; am I missing something?

 

i bought the tools and material for this mod and am now wondering if I should stil do it.. i have a k&n filter already though...any thoughts?
do i still need to remove the elbow

 

You're talking about doing the deckplate, right?

The 3.4 engine is well known for being starved for air on the 4Runners - it's that dern elbow in the airbox....

....wait, is there an echo in here? (look up a few messages )

Yes, you should do it. Just having the K&N in there won't get more air into the engine 'cause the box is starved for air.

And no, you'll want to leave the elbow in place if you do the deckplate. This allows the airbox to go back to more of a sealed state when you put the deckplate back on (think "water crossing").

 

cool midiwall. just nervous bout the whole thing i guess. i have some left over marine grade silicone rubber, will this be sufficiant around the deckplate to keep moisture out...it is marine grade afterall. as you can see i am new to the DIY stuff!!!

 

It'll be fine under one condition...

Some silicone sealer will have a nasty effect on the MAF (the thing just after the airbox that monitors air flow into the engine). The fumes aren't good for it and can foul it up pretty bad. So, if you're going to use what you have then if it doesn't _specifically_ state that it's "sensor safe" (it will if it is) then go ahead and use it, but leave the top of the airbox open and DO NOT START THE ENGINE (or leave the whole airbox out of the truck) until the silicone has completely set (12ish hours).

The alternative is to use sensor safe silicon, which can be foudn at an auto parts store (Napa, Schucks, Kragen, etc).



Good luck! Have fun!

 

didnt know there was such a thing as sensor safe silicon! will probably use what i have and see what happens from there! thanks for the info!