Terrible MPG, loss of power, lean in one bank...please help me

So to start I have a 2008 Toyota Tacoma TRD sport with a 6 speed manual. Bilstein kit at the highest setting and 285 duratracs. Iv tested and done a lot of things for this problem which I have listed below and now I’m looking at the ACIS system. I’m gunna apologize in advance for the length of this post. Iv done a lot to chase and wanted to give anyone reading this as much info to work with as i could. So I have spent countless hours searching and trying to find some answers regarding the ACIS system (air intake control valve system) with absolutely no luck answering what I’m looking for. All I was able to find is what it is and what it does. So I understand what it’s supposed to do and what not. It is supposed to use vacuum to actuat a valve in the intake that changes between two intake paths one shorter and the other longer. Which is supposed to help the engine make better power across the whole power bank apposed to just high end power or just low end power peaks. But I don’t think mine in functioning properly or at all.

So the reason I even began looking at this system is Iv been fighting with a problem of really bad gas mileage and loss of power. (Power loss comes and goes the gas mileage could come and go with it but I wouldn’t know for sure because I don’t have anything to show me MPG in real time). I do have a 3in lift and 285 duratracs so I don’t expect the best mileage and power but deinfelty more than I have. And right off the bat I’m gunna say I do know that the tires affect the speed sensor readings and the speedometer and odemeter and I have already figured out how much it’s off and I do account for that when I figure out my MPG. Around town my mileage seems to be Okay/normalish for the tires and setup. Getting about 13-14 MPG. however on the highway I would expect to gain some mileage without stop and go traffic. And I don’t. I loose mileage which is super weird. And sometimes it really feels like it doesnt wanna do more than 70 mph uphill. What really made me start looking into issues was when I towed my sled last weekend. And all I have is very light open trailer all aluminum and ply wood. maybe weighs 200lbs or so. And then a short track trail sled which weighs at most 600lbs. So I was pulling 800-1000lbs and I only got 8.8 mpg towing that at 65-70 mph on the highway the whole time. I used over 3/4 tank and only went 130 miles. From what Iv seen people get 9-10mpg towing there 5000lbs campers. I was barely towing anything compared to what these trucks are supposed to be able to. And it felt like it was working much harder then it has in the past towing 2 sleds.

So immediately I did all the basic stuff. Changed all fluids, did spark plugs, new intake filter, cleaned MAF, checked for any vacuum leaks (had 22hg at idle). I tryed to check for plugged up exhaust but not sure how thourough my check was. I did a test with engine vacuum and it is supposed to keep losing vaccum towards zero when holding the acceptor at 2500. Passed that test and then hooked my vacuum gauge into the rear o2 port and read the psi and it was bouncing right at zero and revving it hard didn’t get anymore than 1 psi. So that proves from there to the tailpipe isn’t plugged up but maybe the front cat is. I Couldn’t get to that o2 sensor to test so I’m not sure about that.

I tried to read the live data and test that my o2 sensors were functioning properly but thats hard to do because the information everywhere is contradicting for the front o2 (actually an A/F sensor not o2). My front o2 certainly doesn’t show oscillating from .1-.9 Because it is an a/f sensor. And I couldn’t find any support for porperly testing that that is functioning how it should. But both banks stay similar to each other and are at 3.2-3.3 at idle and light throttle cruising and then giving it more gas it comes down into the 2.0-3.0 range. And then punching it give me 1.0v maybe a little over. The rear o2 seems to be normal with engine warmed up holding 2500 rpm they both sit right around .700 with little fluctuation. So im really at a loss right now.

What really catches my attention and tells me something is up is my fuel trims. From what I’m seeing here my bank 2 is lean or the computer is seeing it as lean and is trying to add more fuel. With the engine off and scan tool hooked up I get:
STFT b1:0.0
LTFT b1:0.0
STFT b2:0.0
LTFT b2:11.0
With engine idling or engine braking
LTFT b1:3.0-4.0
LTFT b2:12.0
Driving
LTFT b1:3.0
LTFT b2:8.0

So back to the ACIS system. I noticed that no matter what I did (reving engine, holding certain rpm etc.) I couldn’t get the vacuum actuator to actuat the ACIS system. I used my mighty vac to verify that the diagram in the actuator is still good. So I hooked a vacuum gauge to the line that should be activating the actuator. And then took it for a ride and tryed multiple different scenarios of engine load and rpm and throttle positioning and not once did I get a reading on the vaccum gauge. Which tells me that something isn’t working in that system. (Most likely the solenoid) However idk if it is stuck closed or open or how it is supposed to react when it is good. If someone could look at there truck and see if that has vacuum at idle with an engine warmed up that would help. Or if anyone has or knows any methods that I can use to test that system and find out if it is functioning that would be awesome. I figure if that is stuck open or closed then the way the computer is tuned to run is gunna be messed up either on the high end (stuck closed) or the low end (stuck open, which is probably what it is seein how the low end feels like it’s where I’m loosing power. After 4500 rpm it’s feels like it hits a power band and opens up more still not as much as I would expect out of it though) and could be causing me these issues. But to be honest still wouldn’t solve the fuel trim in bank 2 as that has to be something directly related to bank 2. But any help with this will be super appreciated. Iv spent so much time on here reading so many different things and Iv tried all of them and am now stumped with why my truck is acting like this.

Possible culprits that are left:
-BAD ACIS (solenoid not activating system)
-CLOGGED/BAD INJECTOR(S) (I would think this would give me a misfire or more problems)
-A/F SENSOR FAULTY (don’t know how to determine this and can’t find how anywhere. Always talks about just o2 senor testing but that doesn’t work for our sensors)
-MAP SENSOR (do we have one? I can’t find it or any info on it. How do I test it if we do?)
-FUEL DELIVERY PROBLEM (possible I guess but I wouldn’t think so with how quick it sucks it up)
-FRONT CAT CLOGGED (would think I would have efficiency codes or issues)
-INTAKE/VACUUM LEAK (that only affects one side of the engine??? Or one side more than the other if that’s possible idk)
-EXHAUST LEAK if there is one it would have to be very small and it would have to be at the manifold. I went over the whole exhaust with my hands and did the paper test. No leaks at any joints in the exhaust. Even put my hand all around the manifold with a cold engine running and didn’t feel anything. Also shoved a rag in tailpipe and poked around and listened for any
Exhaust leaking and didn’t find anything.

 

Do you have the stock air filter or an aftermarket type of system?

 

I have OEM right from Toyota. I figure your thinking the air filter oil from an aftermarket could be messing up the MAF. But if the MAF was bad I would think I would see an issue on both banks not just bank 2 wouldn’t I? Or is it possible for that to mess up just one bank?But the MAF has been a thought. That’s why I gave it a good cleaning and even checked to make sure the air temp was right just Incase the temperature parts of the sensor was messing things up.

 

Anyone? I’m about tearing my hair out over here trying to figure this out...

 

If you think you are running lean then smoke it.

 

Like a smoke test for vaccum leaks? Not a bad idea. Would help rule out any leaks for sure. I thought if I had some kind of leak I would see it in my vaccum test but maybe the leak is to small to catch that way. The reason I think it’s running lean is because the fuel trims show positive numbers so that means it’s trying to compensate and add more fuel which would mean lean. Correct?

 

Correct. You unhook the battery recently? These engines run like crap after a battery swap for a while

 

OK, after glossing over your original post a couple of things POPPED out at me.

-Your KOEO shows bank 2 sensor stuck, it should be ZERO like the others.
-The ACIS system is more then likely disabled due to the system being in limp mode or DTC's stored in memory.
-You have some sort of scan device that reads fuel trims, have you checked for codes yet?

The first thing I would do is swap the A/F sensors side to side and see if the fuel trim problems switch to bank 1 - disconnect the battery and hold the cable ends together for 10 minutes to reset the adaptives before you start the engine and test drive it.

If the fuel trim problem moves with the sensor, replace it.

 

Back like 2-3 weeks ago when I cleaned the MAF I did do an ecm reset. But I think by now it’s through the re learn. Also I think it actually ran better on learn mode at first.

 

I’m not exactly sure what KOEO is to be honest. But I as well thought it was weird for it to be sitting at anything but zero. I do have a scan tool. And Iv tryed in multiple occasion. No codes at all. None pending no permanent no dtc.

As for switching the sensors that is a super good idea thankyou. I never thoght to do that. But if it switched to other bank then we for sure know something is going on there. Good idea. Now to find a way to get in there and get those sensors out LOL

 

KOEO Key ON Engine OFF.

If swapping the sensors does not change anything, start looking for an exhaust leak on bank 2, at or near the A/F sensor.

 

Okay I will do that. Thankyou very much for the help I appreciate it. Since our sensors our actually a/f wideband sensors and not o2 sensors. Do you know if there is a way to test that they are operating properly with scan tool live data. Seeing how you can’t just watch for it to oscillate from .1-.9 Because it’s not an o2 and the voltage readings are actually like 3.3 to 1.0v.