07-17-2018, 10:42 PM
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#16
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Quote:
Originally Posted by curryT4R
Fair enough! In my defense, I don't actually own a 3rd gen yet LOL, so I was not aware of the single exhaust. I was just going off my experience as a Lexus master tech for the last 5 years. So there is only one cat and one sensor? Unlike the 3MZ engine which as 2 cats, one off each exhaust bank.
It very well could be a bad A/F sensor, just wouldn't be the first thing I would replace. Trust me, I hate P0171s as well! It's either really simple or very complicated.
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One exhaust sensor before cat or cats and one after on all years. Two versions of the single exhaust-'96-'00 Federal with one cat and Cali. '99 and '00 and Federal '99-'02 with two cats in line off the single exhaust bank. Two-cat systems used the wideband A/F sensor in front.
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'99 4Runner SR5 5spd 3.4L V6 4WD(U.S), original '99 Talls in front, OME 906s in back, Hella fogs, Trekmaster shocks in front, Billy in back, no running boards, FIAMM horns, Alpine sound, Michelin LTX M/S2's, owned since new.
'97 HiLux SW4 5spd 4WD(Japan model bought in Brazil assembled in Argentina, very close to a 3.0 4Runner/Surf)
'71 FordWillys Jeep CJ5 (with straight six Ford Maverick 3.0 liter engine--lives in the mountains north of Sao Paulo Brazil)
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07-18-2018, 10:19 AM
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#17
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Location: Houston, TX
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Quote:
Originally Posted by TheDurk
One exhaust sensor before cat or cats and one after on all years. Two versions of the single exhaust-'96-'00 Federal with one cat and Cali. '99 and '00 and Federal '99-'02 with two cats in line off the single exhaust bank. Two-cat systems used the wideband A/F sensor in front.
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Makes sense now. Thanks for clarification.
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07-18-2018, 11:55 AM
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#18
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Quote:
Originally Posted by curryT4R
Makes sense now. Thanks for clarification.
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Welcome to the forum. Looking forward to your participation.
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'99 4Runner SR5 5spd 3.4L V6 4WD(U.S), original '99 Talls in front, OME 906s in back, Hella fogs, Trekmaster shocks in front, Billy in back, no running boards, FIAMM horns, Alpine sound, Michelin LTX M/S2's, owned since new.
'97 HiLux SW4 5spd 4WD(Japan model bought in Brazil assembled in Argentina, very close to a 3.0 4Runner/Surf)
'71 FordWillys Jeep CJ5 (with straight six Ford Maverick 3.0 liter engine--lives in the mountains north of Sao Paulo Brazil)
My Backyard Frame Swap
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07-19-2018, 07:00 PM
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#19
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Location: Baltimore
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Took it to the dealer because I have no time to mess with it. They said they found two torn “mass air flow sensor tubes” and that these tubes would cost $100. Anyone have any idea what tubes he may be referring to?
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07-20-2018, 10:04 AM
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#20
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Quote:
Originally Posted by Bt08231
Took it to the dealer because I have no time to mess with it. They said they found two torn “mass air flow sensor tubes” and that these tubes would cost $100. Anyone have any idea what tubes he may be referring to?
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I have no idea what a "MAF sensor tube" is. Unless they mean the actual MAF sensor wires (the part that we typically clean when they get dirty).
Check those and see if they are torn/broken.
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09-22-2018, 11:12 AM
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#21
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Don't mean to thread jack but I was trying to find an answer without posting. I did get the P0171 code previously but after cleaning the MAF sensor it went away. Changed the O2 sensors, Fuel filter, Coils and sparks too. I still get a random hesitation and misfire with little power. Have to pull over and re-start the car but no code. Suggestions?
Quote:
Originally Posted by MStudt
Here are possible issues.
Diagnostic Codes
P0171
Confirmed Fix
225 - Mass Air Flow (MAF) Sensor
9 - Engine Air Filter, Mass Air Flow (MAF) Sensor
4 - Oxygen (O2) Sensor(s)
2 - Fuel Pump
1 - Front Oxygen (O2) Sensor
1 - Vacuum Leak
1 - Fuel Injector(s), Mass Air Flow (MAF) Sensor
1 - Cruise Control Vacuum Line
1 - Intake Manifold, Mass Air Flow (MAF) Sensor
1 - Mass Air Flow (MAF) Sensor, Throttle Body Cleaning Procedure
1 - Mass Air Flow (MAF) Sensor, Mass Air Flow (MAF) Sensor O-Ring
1 - Exhaust Pipe, Mass Air Flow (MAF) Sensor
1 - Air Intake Tube
1 - Mass Air Flow (MAF) Sensor, Throttle Body
1 - Air Fuel Ratio (AFR) Sensor
1 - Engine Vacuum
1 - Oxygen (O2) Sensor, Bank 1 Sensor 2
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10-23-2018, 07:33 PM
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#22
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Has anyone replaced the upstream O2 or called the fuel/air sensor while trouble shooting this issue? I am trying to do it however the plug sits on top of the transmission and I cannot figure out how to get the darned thing out without dropping the trans or lifting it off the frame.
Manual 4wd 2000 runner.
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10-23-2018, 09:08 PM
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#23
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Replacing this resolved my 0171 code...
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2001 Limited 4WD - 346+K - SunfireRed\Thunder Cloud; - 265/75/16 Michelin A/T2s - Fat Pat's 1.5" BL - StopTech ANGLED rotors - In series 699 trans cooler, New Yota1 transmission, All new OEM suspension front to rear.
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10-23-2018, 09:25 PM
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#24
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Quote:
Originally Posted by shaneclark562
Has anyone replaced the upstream O2 or called the fuel/air sensor while trouble shooting this issue? I am trying to do it however the plug sits on top of the transmission and I cannot figure out how to get the darned thing out without dropping the trans or lifting it off the frame.
Manual 4wd 2000 runner.
Sent from my SM-G950U using Tapatalk
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Actually, I had a P0171 that I was able to resolve by swapping the A/F sensor, even though a self-described "Toyota Master Tech" on here told me it could not be the cause. The FSM does list it as a cause:
Quote:
Air induction system
Injector blockage
Mass air flow meter
Engine coolant temp. sensor
Fuel pressure
Gas leakage on exhaust system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
PCV valve and hose
ECM
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I have the same rig ('99 and '00 are clones) and I think I got that clip undone through the shifter hole. I then left it unattached without further problems. Then you can just unbolt the sensor, throw it over the top, and undo the connection where it hangs down on the other side.
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'99 4Runner SR5 5spd 3.4L V6 4WD(U.S), original '99 Talls in front, OME 906s in back, Hella fogs, Trekmaster shocks in front, Billy in back, no running boards, FIAMM horns, Alpine sound, Michelin LTX M/S2's, owned since new.
'97 HiLux SW4 5spd 4WD(Japan model bought in Brazil assembled in Argentina, very close to a 3.0 4Runner/Surf)
'71 FordWillys Jeep CJ5 (with straight six Ford Maverick 3.0 liter engine--lives in the mountains north of Sao Paulo Brazil)
My Backyard Frame Swap
Last edited by TheDurk; 10-23-2018 at 09:31 PM.
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10-23-2018, 09:37 PM
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#25
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Real Name: Totyota
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Mine was a combination of vacuum leaks and a dirty MAF.
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2002 limited 4runner, Supercharged/7th injector/2.2 Pulley, Level 10 bulletproof transmission, 3" lift with 2.5 Fox Coilovers up front, Fox 2.0 reservoirs in the back, Toytec 3" springs in the back, Rokman lower links, Frontrange upper links, 285/75R16 Wildpeak ATW3's, SRQ Retrofits, Flowmaster 50 series SUV, New leather seats and steering wheel wrap, 4xinnovations bumper up front.
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10-23-2018, 10:34 PM
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#26
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I just resolved my p0171 code that popped up the other day. I spent $9 on some CRC Maf sensor cleaner and about 15 minutes and that cleared the check eng light and error code. It also ended my bad pinging (worse as the temps rise). Will be replacing ign wires with NGK, new plugs, new denso O2 sensors, and new oem pcv valve.
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'96 T4R SR5 V6 Auto 2WD 329,000 miles
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10-24-2018, 04:49 AM
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#27
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vacuum leak, too bad there are a billion possible places!
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08-04-2020, 06:21 PM
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#28
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I'm getting this code as well. I believe it started when I replaced my valve cover gaskets. I cleaned the throttle body and IAC valve. I WAS getting a high idle as well.
Things I've Checked/Replaced:
-checked the TB gaskets.
-replaced MAF
-replaced both O2 sensors
-replaced the charcoal canister thing (forget what it's called)
-replaced a torn air boot
-checked the vacuum lines & replaced a few
-replaced throttle position sensor
-replaced fuel filter
After replacing the Throttle Position Sensor, my high idle is no longer an issue. However, the code was triggered AGAIN today!
I think it's one of 4 culprits: 1) over cleaning the throttle body and somehow it's not closing all the way anymore or 2) idle air control valve is shot or 3) the charcoal canister i bought via ebay is bad or 4) bad fuel injectors (242k miles on original).
I have seen decreased MPG and I'm getting a stronger smell of gas outside the vehicle.
I have purchased reconditioned fuel injectors (MotorWest Performance; recommended by Timmy). Bought a used IAC valve fr ebay. Guess I'll start here.
Any input?
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'98 4Run SR5 v6 4x4-Orig Owner
Manual Transmission
Bilstein 5100 (front/rear)
OME 890 Springs (rear)
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08-04-2020, 06:50 PM
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#29
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Join Date: Oct 2014
Location: Citrus Heights, California
Age: 36
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Real Name: Jerod
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Quote:
Originally Posted by psea17
I'm getting this code as well. I believe it started when I replaced my valve cover gaskets. I cleaned the throttle body and IAC valve. I WAS getting a high idle as well.
Things I've Checked/Replaced:
-checked the TB gaskets.
-replaced MAF
-replaced both O2 sensors
-replaced the charcoal canister thing (forget what it's called)
-replaced a torn air boot
-checked the vacuum lines & replaced a few
-replaced throttle position sensor
-replaced fuel filter
After replacing the Throttle Position Sensor, my high idle is no longer an issue. However, the code was triggered AGAIN today!
I think it's one of 4 culprits: 1) over cleaning the throttle body and somehow it's not closing all the way anymore or 2) idle air control valve is shot or 3) the charcoal canister i bought via ebay is bad or 4) bad fuel injectors (242k miles on original).
I have seen decreased MPG and I'm getting a stronger smell of gas outside the vehicle.
I have purchased reconditioned fuel injectors (MotorWest Performance; recommended by Timmy). Bought a used IAC valve fr ebay. Guess I'll start here.
Any input?
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I can provide a bit of diagnosis and thoughts on your list of culprits. A P0171 can be grouped into two large culprits, a sensor pertaining to fuel or air delivery to the engine (uncommon) or a leak in the air system causing unmetered air to enter the engine (most common).
1) Over cleaning the throttle body usually results in a clogged IAC valve when deposits slip through the holes on the bottom of the throttle body which would result in high idling, poor idle when hot on a long drive, or intermittent stalling. I've yet to hear of one throwing a P0171 code.
2) See answer 1 above.
3) The charcoal canister would not throw a lean code unless the vacuum lines themselves are leaking air, or the unit was somehow cracked or compromised. A clogged charcoal canister will normally throw EVAP codes. I would say this is unlikely.
4) Bad fuel injectors, or my top suggestion of bad fuel injector o-rings could be the culprit. Trust your nose, if you are smelling unburnt fuel, that means there's a leak downstream of the injectors. Fuel smell is never a normal thing and should be addressed immediately. A bad o-ring on the fuel rail or injectors themselves can also cause un-metered air to enter the engine and throw a code. If you are smelling a combination of un-burnt fuel AND a sulfur like smell, it's and exhaust leak between the cylinder heads and the first catalytic converter, I just took care of that on my 4Runner.
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08-04-2020, 10:43 PM
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#30
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Sounds like you IAC is the only thing, I'd give it a shot. Mine was like $50 (off amazon iirc, was OEM) and took me maybe 30-40 minutes all said and done. Just don't forget the gasket.
Unless you have an 01-02. One of the small changes to the engine bay was making the throttle body and IAC integrated as one unit, and they're MUCH more expensive too replace. You could clean it, but personally I figured why not replace it if it's so cheap and at such high miles? Gonna need to be done eventually, and if it's lasted 200k so far ~~
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