2000 4Runner Limited
Auto Trans
V6

Ok, Took the Yota to Advanced Auto...Code they said read that I needed new Fuel Filter/ and or Dirty Injectors.

Took the Yota to Autozone, and they pulled a PO171...
This is how the print out reads.

Definition
BBAir/Fuel mixture system lean bank 1
(cylinder number 1 denotes bank 1)
Probable Cause
BB1 - Low Fuel Pressure
BB2 - Faulty MAF/VAF sensor * What is VAF Sensor? *
BB3 - Cylinder misfire condition
BB4 - Faulty HO2S/AF sensor * Not sure what this is...O2 sensor? *
BB5 - Large Vacuum leak


-Now, Sometimes when I start it, it will turn over a couple times before it fires up, like maybe not enough fuel.
-It has never stalled, or acted like it isn't getting any power, it runs fine, great in fact other than the CEL is making my MPG suck.
-It doesn't stutter, or make any hiccups.
-They idle is nice and constant all the time, my experience with vacuum leaks it that it makes the idle kinda jumpy.

Please someone who can figure this out help me...I don't want to go and buy a bunch of parts that I don't need. I really can't believe that it is a huge problem due to the fact that it is running so great.
Thanks guys....

William

 

How do you clean and what would I use to clean my Mass Air Flow Sensor, I am throwing a Code PO171 and that is one of the "causes" Autozone gave me.

 

Pretty easy to do, I think you'll notice a vast improvement if you haven't done it in a while:

http://www.top4runners.com/ja/cleanmaf.html

https://www.yotatech.com/forums/f2/maf-cleaning-165411/

 

Think I got it figured out, I bought some of the CRC MAF cleaner, and seafoam and cleaned the MAF, then poured Seafoam in my intake through some vacuum line.

 

Hey man, thanks for that link. I think I got it taken care of. I was throwing a code, so I bought all the stuff and cleaned the MAF and Seafoamed through an vacuum line. Running better already after burning gas for about 10 miles. and the CEL hasn't come back on yet.
Again, thanks man.

 

Ok, Well after about 20 miles of driving the light came back on......any suggestions people?

 

IS this little ball thing at the end of the wires suppose to be there? Or is that what you try to clean off. I know....sorry....newb question.

 

Got the same code 2 weeks ago from Auto Z. My problem was a vacuum leak. Easy to find with starting fluid sprayed lightly around all vacuum lines and vacuum devices. Avoid ignition sources, ether burns GOOD. Other option is go to a shop where they have a "smoker" device to hook to your vacuum system to quickly find leak

 

The code you are throwing is for a failed/failing O2 sensor, bank 1 -- ie, before the catalytic converter. Had this same issue, same code. I cleaned my MAF sensor (not knowing it was the O2 sensor) and the code went away for awhile. And like you, it came back. Easy DIYer.

Do a search on the code your throwing, many people have had this issue.

Chris

 

Thanks,
Ya, I just cleaned the MAF Senso again, come to find out, I didn't look in the little tube and see the *small* wires, I was spraying that two wire thing with the bulb look on the end, so I get them nice and shiny again, light been off for a day now.
I was planning on going and changing out the O2 Sensor though, looks like original, and what the hey, might as well.
Thanks guys.

 

By the way, VAF stands for Vane Air Flow [sensor] (usually you see it listed as "VAFS") - kind of like MAFS (Mass Air Flow Sensor). VAFS is usually found on older vehicles with a "flapper" type VAFS at the airbox opening.

And on another note I got my 02 sensor from urdusa.com for a good deal a couple years ago.

 

Had the same issue on my wife's 2000 4Runner. Cleaned the MAF, code went away for a day or so, then it came back. Said to hell with cleaning the damn thing and bought a new OEM unit for about $120 from a dealership online, code went away and hasn't come back in the 4 months since.

 

I would be careful about just going out and buying new parts before actually finding out what is causing the issue. I have been struggling with this problem for about a year now and still have not been able to fix it. First I cleaned the MAF and did sea foam, then I bought a new O2, then a new MAF, new Fuel filter, and my CEL is still on. Don't go do what I did and burn $3-500 trying to fix it and end up stuck. Get the FSM and go through step by step to try and diagnose the problem code first and save some money.

Here are a few other issues that it could be:

1) Faulty injector
2) Bad fuel pump
3) Clogged fuel filter
4) Bad ECM (I hope it's not this because it is expensive)

 

Well, I did it on Sunday, Sept 20th, and still no problem, plus start up is way better, used to turn for like 4 5 or 6 times before it started, now its on 2nd , 3rd turn. With luck that did it, I mean for real guys, this is a great rig, really taken care of, I feel as though i stole it I got it for only 7k with 120 on the dash, in my opinion that is great for a yota, these things last forever and a day if taken care of.

 

I started getting this code a couple of weeks ago. I just tried cleaning the MAF so I'll see how it goes tomorrow. Could the colder weather be causing this to happen? I think it may possibly be my fuel filter too because it has never been changed in 10 years.

 

Check engine light MAF - YotaTech Forums


read this thread. I had the same problem last week. Dropped 200 dollars in sensors and come to find out it was a missing hose behind my super charger.

BTW if your in LA area i have a mass airflow sensor and o2 sensor that are good. Trade or sell.

 

Still no CEL after cleaning MAF. My fuel filter is original and I'm thinking of changing that anyways. Only problem, is that I don't know where it is. Book and web say behind the alternator, but I couldn't find it there unless I'm blind. It's a '99 Ltd. can anyone enlighten me?

 

Fuel filter is mounted to the frame on the drivers side. What book and web are stating behind alternator? Is that a Canadian thing

 

I have the Haynes Book. It was actually my bro-in-law that stated that and he had a few beer into him, so I'll take a look myself.

 

This may not help the original poster much, but just to clear up a common error. All the exhaust system sensors on these trucks are bank 1 because we don't have factory dual exhaust. You will only see a bank 2 lean code on a vehicle with dual exhaust from the factory and 4 sensors (two for bank 1 and two for bank 2).

On our trucks the front sensor is called sensor #1 and the rear sensor is sensor #2 but both are bank 1.