Aftermarket intakes on 1st Gen 3.4 5VZ-FE engines- see this

Installing an aftermarket air intake and struggling with the bullshit problems that follow seem to be a right of passage with owning a 1st gen Taco, and like so many other owners here, I became a man in that respect.

In 2012 I removed the stock intake and installed a K&N kit and had no problems whatsoever for 6 years. This past winter I removed the K&N kit to make room for an auxiliary battery; other write-ups I'd seen had the second battery installed where the ABS actuator sits in my engine bay so that wasn't an option. After removing the K&N kit, I decided to install a Spectre Performance modular kit. That was a mistake.

I spent the next four months dealing with CEL P0171 codes, shitty gas mileage and lousy performance. Gas mileage dropped 8mpg in the city in some cases and averaged about 13mpg on the highway. Luckily this year I wasn't required to get emissions tested in Washingto State because I would have failed. Finally I said fuck this shit and removed all of my auxiliary battery components and Spectre intake and reinstalled a factory intake from new parts I found on eBay and the stealership.

Performance increased, fuel economy doubled, and the CEL went off and hasn't come back on since. Want more proof? Have a look at the fuel trims in these screenshots. Aftermarket intakes are dumb unless you are racing, have a supercharger, or have a carbureted engine.

 

It's strange but, the 5vz motors seem to run just perfectly happy with the stock intake and other than sound, you really can't improve on them for n/a applications.

Granted all the videos and written articles I've seen in intakes, air filters, and oem designs, it really matters on design on how efficiently air is drawn into the motor. The only thing i can chalk up the stock design to operating so well is the air filter box tapered design and how big of a surface area the filter provides to draw air from. Fun video I watched recently on this matter pretty much proves these things here.

https://youtu.be/EkpsydS8JXI

 

This video really is cool, thanks for posting. It really is strange, agreed. What's even more interesting is that even after modifying the aftermarket intake around Christmas time last year, after getting the unmetered air leaks fixed, the truck ran fine for a few months. After coming back from a two week road trip from Washington through Oregon, Idaho, Utah, Arizona, California, and back home (about 3600 miles total), I made a slight change in the angle of the intake tube and everything went south. Since then I had one problem after another. I managed to get it running great again after changing the filter for another reusable one with a different shape, but then suddenly for no reason at all it started throwing codes.

I think every Tacoma owner in the forums that has written about this has come to the same conclusion and went back to stock. All of them have said the same thing; not one problem since. Its true; the manufacturer spends millions of dollars in R&D to make it run optimally, trying to change things based on some bro-science you read in a forum almost always makes things worse.

 

Yea... it's funny but it holds true. Toyota did their research.. from that you gotta wonder how much research aftermarket companies to in order to "improve" on that deaign. Dyno testing? Real world testing etc...

It goes the same for any aftermarket performance parts, headers, cat back systems, cams, super chargers etc...

 

Yeah, I wish I had the stock air filter parts for my 2002 Tacoma, I hate the loudness
of the thing that the former owner put in there...



-Mike

 

I do have to admit I like a couple of things aftermarket intakes do like a little resonating from the intake and the cleaner look. However its more asthetic than performance. Maybe theres a way to mold the best of both worlds and hybrid something together but it may just be wishful thinking

 

It looks like the tube for the MAF is bigger than the stock intake. If you put that in a larger tube more air is going to flow into the engine than the computer is counting on. That could be contributing to your lean codes.

 

It's possible... though the amount of air flowing through at partial or full throttle would still be the same given the limiting factor is the throttle body itself no?

 

Also, without tuning the ECM the EFI auto-adjusts to be optimal. That's one main reason the aftermarket intakes provide no value or gains

 

The air in the tube will be moving slower since its bigger registering less air, regardless of throttle position wouldn't it? I'm no expert. Im just speaking my mind.

I believe the MAF sensors work on temperature. Theres one probe that reads ambient temperature and the other reads temperature drop (its heated to whatever temperature and it measures the cooling effect). If the intake tube is larger, the air is going to move slower for the same demand, meaning the sensor is going to register less air than is actually passing by.

 

You CANT change the tube size from the original stock size. You are guaranteed to get a lean codes
and lots of problems. (Air Fuel Ratio)

BTW, I have 560,000 miles on my K&N kit, never had a problem EVER, except for getting a new filter under warranty at 450,000 miles, I’m happy with what I have.

 

Both points true. The computer to some degree has set parameters to work within and will adjust to the motors needs within what's programmed .

The velocity at wich the air moves is also true in the sense that in a larger tube, the sensor won't have the same air velocity moving through it therefore cooling at a different temp. This makes sense for a leanrunning condition. If the sensor picks up less air flow through the sensor due to its larger diameter it would think there's not much throttle being given therefore not need as much fuel, when in reality there's more throttle being given drawing more air but not given enough fuel.

Damn.... guess I learned something today

 

AND I Get 25 mpg at 65mph with the K&N

 

I average about 22 but I drive considerably faster paced on the highway... I have the oem intake and filter with a magnaflow catback.

 

Yup that’s good, I’m a 4x4 and sit higher and running a supercharger, so you will do better at higher speed of course.

 

The OP problem is all related the the incorrect tube size, that’s all!!

“DO NOT CHANGE ANY OF THE STOCK INTAKE AIR DIMENSIONS”

 

I imagine the ECU takes the throttle position into consideration as well.

You know what they say, its a sad day when you don't learn something new!

 

I got rid of my stock setup after installing the K&N in 2012, and wished I had them still a month ago. Good thing Amazon and eBay exist because instead of spending $600 like the stealer wanted for the intake tube, resonators and airbox, I only spent $37 for the tube, $66 for the airbox, and $180 for the resonators and air filter from Toyota of Bellingham. That noise is annoying though, I agree.

 

I don't know, I wish a Toyota engineer would jump in and explain it. All I know is that the MAF expects a predetermined volume and velocity of air, which the stock 2.7" tube creates in conjunction with the OEM filter and airbox. The aftermarket kits affect this expected air volume and velocity, and once it starts happening (CEL warning indicators), there is little you can do except reinstall the stock equipment. I had considered getting a MAF recalibration module from URD, but that was a few hundred $$ and that's when I pulled the band-aid off this festering wound and went back to stock.

It looks cleaner, sounds better, and it gives piece of mind.

 

I tried smaller tubes, even the original K&N kit that I used to have and nothing worked. Going back to stock was easiest.