Help!!! P0171!!!

[Baja Runner]

I'd still bet money its the MAF. It sounds like you might need to buy a new one.

You need to test the O2 sensor. If its old then that might be your problem but the P0171 usually is MAF related.

 

[whodini]

Had the same problem

The guy I bought the truck from had a k&n air filter before I bought it and I just pulled it out after I got the same code. I also tried cleaning the maf but still got the code. I replaced maf code went away and hasnt come back in over a year. Don't get it from the stealer I can't remember where I got it from (online) but it was half the price (make sure it doesn't say refurbished) You could try cleaning again, But it is sensitive.

If that fails get someone to check the o2 sensor.

 

[ludog]

You prob need a new MAF, alot of people put way to much oil in the k&n filters and the oil gets caked on the MAF and gives it bad readings. check for a vac leak, get some break parts cleaner and start your engine get to normal running temp and spray around vacume lines if your engine starts to bog down there is your prob area.

 

[fightman80]

I'm not running my K&N yet.....been waiting to solve this little problem before introducing another variable.

I took the truck to my brother in law yesterday, he's a heavy duty mechanic. We looked over the truck, and he also thinks it's the 02 sensor. We tried to loosen the nuts off, so that I could do it with ease when I get the sensor, but the nuts ended up stripping! Our next plan of action, will be to remove the cat, try to get the sensor off while the cat is on the work bench, and if necesarry, cut the studs, and weld in some new ones. If that don't work, I'll be buying a new Cat.....uhh....

We won't get a chance to work on it until next weekend though....as he is steady nights all week, so I'll keep you guys posted on this.

 

[BrianSD_42]

so fight man, just to clarify you never spayed any k&n oil on that filter you installed, it was completely dry upon running it?

if you did get that light because of the filter, it should be possible to clean the maf once disassembled.

I dont think maf fail is very common

 

[TheDurk]

Yeah, they tend to strip. The good news is that the studs are a whole lot harder than the nuts, which tend to just crumble under pressure. I just kept using smaller sockets rammed onto the nuts, and a small pair of vice-grips, and eventually they came off in pieces. Then i cleaned up the threads with a wire-brush.

I'd work really hard before I resorted to pulling the cat.

 

[Baja Runner]

Haha.. Well I think a number of us have stated that its most likely the MAF still. But go ahead and throw your money on the O2 and cat if you want.

 

[fightman80]

Guys, we checked the MAF and it seems to be working fine. It is also spotless inside, even before I cleaned it. Not that I don't respect all of your opinions, because I do, but so far, I've had one parts guy, one Mechanic, and some of you pointing to the 02 sensor. I don't want to buy a MAF if it's just the 02 sensor, which, as far as I know, is probably worth the same amount of money.....

Durk, I'll probably give it another go on Tuesday, and try to same my Brother in Law some time on the weekend.....We did try to use smaller sockets, but still no go....maybe I'll try to do what you suggested, and just work at it, until nothing is left except the bolts!

As for the K&N, like I said, it's never been installed yet. I still have my FRAM in there right now. Like I mentionned before, I'm not installing it until I get this issue figured out.

Thanks for all your replies, and I'll keep you posted on what transpires.

 

[jlcrss]

I am just tuning in to this thread. Mine went off today. I have 2000 and the P0171 code came up. My truck is also starting a little hard and using a lot of gas.

 

[MrBobDobalina]

How many miles has it been since the o2 was replaced last that you know of? If has been significant, it probably wouldn't hurt to just replace it regardless...When they are new, it always seems to imporve mpg at least...

 

[jlcrss]

I have 79k I think the sensor has never been done.

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[jlcrss]

Does this look dirty? Is that brown stuff suppose to be there?

I can't get the MAF off of the air box because the GOD DAMM screw is stripped!!!! WTF

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[TheDurk]

The important thing are the two extremely fine 'hot wire' sensors in the long tube.

The brown bulb is normal, but that is the temperature sensor. It should also be cleaned, but it is not as critical as the MAF itself.

You ABSOLUTELY have to have it off the tube to SEE the sensor wires, let alone clean them.....

.....because you kave to do this:

...otherwise you are just wasting your time. Here is some insight written by a Toyota tech that accompanied these photos:

I believe all you need is to clean your MAF (Mass Airflow) sensor. This is a common problem on many late model Toyota's, and when the vehicle is diagnosed at the dealer or any other repair facility, they tend to sell you a new MAF, and a new Oxygen Sensor. You end up paying close to $500, by the time you walk out of a repair shop. The MAF becomes dirty from age and the sensor wires can no longer accurately tell how much airflow is entering the intake, thus causing the engine's computer to lean out the fuel mixture.

[and.....]


The entire sensor has to be removed from the air cleaner box, and all (3) of the sensor wires cleaned. About 90% of late model Toyota's with a P0171 (lean condition) code, are due to contaminated MAF sensors. The only other possibilities are a vacuum leak in the PCV (Positive Crankcase Ventillation) system, a plugged fuel filter, a faulty MAF sensor, a faulty PCM (Powertrain Control Module), or a faulty Oxygen Sensor. The correct form of diagnosis requires a factory level scan tool in conjunction with an automotive oscilliscope,

Read more: Toyota Questions - 1999 toyota 4 runner computer code says bank 1 running lean ... - JustAnswer Toyota Questions - 1999 toyota 4 runner computer code says bank 1 running lean ... - JustAnswer

This is good stuff.

 

[jlcrss]

The important thing are the two extremely fine 'hot wire' sensors in the long tube.

The brown bulb is normal, but that is the temperature sensor. It should also be cleaned, but it is not as critical as the MAF itself.

You ABSOLUTELY have to have it off the tube to clean it.

I was able to shoot the cleaner up into the sensor where the MAF is. Is that sufficient or do you actually need to clean it with something physical?

 

[TheDurk]

I was able to shoot the cleaner up into the sensor where the MAF is. Is that sufficient or do you actually need to clean it with something physical?

You don't want to touch them (the MAF wires) at all with anything physical. You could easily ruin the MAF. But you do need to see them to direct the cleaning spray and blast the crud off--and also to tell whether you have gotten them clean. It can take a few repeats to get the job done. The wires should be silver bright.

 

[jlcrss]

I got it off and replaced the screw s got it clean im probably going to do threw o2 sensor next I'm dreding getting those bolts of

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[fightman80]

Does the MAF on my 98 come apart like that?? If so......I definately didn't clean it that well!!! When I took mine out of the intake tubing, it kinda looked like the front of a jet engine....in that it had a cone looking thing at the end of it. Can I take mine apart like that??? The last car I did the MAF on, all I had to do was pull it out, and spray inside...no disassembly involved!

I just bought the 02 sensor today, but if my 98 MAF needs to be disassembled like that to clean it....I'll definately try cleaning it again!

 

[8sm]

Hey Fightman whatever you do, becareful with it when cleaning. Those things are expensive. I found this online perhaps you can test the MAF using an Ohms volt meter.



Inspect the MAF sensor for any dirt, dust, or other debris. Make sure that the sensor is free of any contaminants.


Set your voltmeter to the Ohms setting and measure the resistance between terminals THA and E2. To do this, place one lead on the voltmeter on the THA terminal, and another lead on the E2 terminal. The reading should be at or near 0. If it is, move on to step 3. If it is not, your air flow meter is faulty.


Turn the ignition switch to the "on" position in your vehicle.


Set the voltmeter to "volts" and connect the positive lead to the VG terminal and the negative lead to the E2G terminal.


Blow into the air intake air flow meter and check to make sure that the voltage fluctuates. If it does, your mass air flow sensor is working properly. If the voltage does not fluctuate, then your air flow meter is faulty.

 

[quicksilvr]

Does the MAF on my 98 come apart like that?? If so......I definately didn't clean it that well!!! When I took mine out of the intake tubing, it kinda looked like the front of a jet engine....in that it had a cone looking thing at the end of it. Can I take mine apart like that??? The last car I did the MAF on, all I had to do was pull it out, and spray inside...no disassembly involved!

I just bought the 02 sensor today, but if my 98 MAF needs to be disassembled like that to clean it....I'll definately try cleaning it again!

Fightman, you have the older style MAF. None of the previously posted pictures accurately represent your part. Those pics are all of the '99 and newer MAF.

You still need to take your MAF all the way out of the truck, and then with a flashlight, look down inside it very closely. You'll be able to see the two extremely thin wires that need cleaned. Don't touch them, just try to blast them with the MAF cleaner. I remember that I was able to get my '96's nice and clean, but you have to spray in just the right place. It's not as easy as the '99 style. Make sure you don't hit the wires with the end of the red spray straw.

 

[TheDurk]

Fightman. I apologize for letting my response to the newbie with the 2000 clutter up your thread. All that was indeed the newer sensor design. But both the threads in the sticky address the early design.