P0171 (1 Viewer)

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Joined
Jun 24, 2020
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Location
Oregon
Hi everyone. I have come to get knowledge on my 2000 lc because I have a P0171 code and I can’t figure out what it is. I have replaced all O2 sensors and had reset but code came back 2 days later. I have had a evap leak before and I know I did not have the best mechanic in town. What would you guys try next. I haven’t gotten to cleaning the mas airflow sensor yet but I do have some readings from it. I uploaded 2 photos the one with .5lb was at idle. And the second photo is at 2000rpm. Thanks in advance!

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Running the Active Tests in Techstream would be immensely helpful. Otherwise, you’re pretty much shooting in the dark, throwing money and parts at guesses. See here: http://4runnerclub.com/i/4r_files/f...7toyrm/07toypdf/07rmsour/4runnerr/0060028.pdf

Based on what you provided above, I’d check the air intake for leaks, vacuum/evap hoses for leaks, and clean the MAF. I think the MAF readings you have at 2k RPMs are supposed to be lower (0.71-1.0 lb/min) and at idle are supposed to be lower (0.18-0.3 lb/min).
 
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Running the Active Tests in Techstream would be immensely helpful. Otherwise, you’re pretty much shooting in the dark, throwing money and parts at guesses. See here: http://4runnerclub.com/i/4r_files/f...7toyrm/07toypdf/07rmsour/4runnerr/0060028.pdf

Based on what you provided above, I’d check the air intake for leaks, vacuum hoses for leaks, and clean the MAF. I think the MAF readings you have at 2k RPMs are supposed to be lower (0.71-1.0 lb/min) and at idle are supposed to be lower (0.18-0.3 lb/min).
Thanks for the info. I have a feeling it’s going to end up being a vacuum leak but I am going to go to the store and get some mas air flow sensor cleaner. Thanks again!
 
Diagnose vacuum leaks and clean the MAF sensor with some MAF cleaner. Replace air filter if needed.
 
Check all the evap hoses in the engine bay. They are easy to replace. I had the same code, new o2 didn't solve it. For me the hose in the rear passenger side of the engine compartment was all cracked at the ends. Went to autoparts store and got a similar sized hose. Solved the issue. I'd go through and take all the evap hoses off one by one and inspect them. Some you'd need to get from the dealer. The majority you can get off rockauto for a reasonable price. Those little tiny ones on the pass side also tend to crack.
 
Check all the evap hoses in the engine bay. They are easy to replace. I had the same code, new o2 didn't solve it. For me the hose in the rear passenger side of the engine compartment was all cracked at the ends. Went to autoparts store and got a similar sized hose. Solved the issue. I'd go through and take all the evap hoses off one by one and inspect them. Some you'd need to get from the dealer. The majority you can get off rockauto for a reasonable price. Those little tiny ones on the pass side also tend to crack.
Thanks for the tips I am going to throughly inspect the evap hoses and hopefully I find something. And quick question, will it be easier to spot something when the car is on? Thanks
 
Thanks for the tips I am going to throughly inspect the evap hoses and hopefully I find something. And quick question, will it be easier to spot something when the car is on? Thanks

Just pull them off one by one. If the ends or any part is cracked it needs replacing.
 
Running the Active Tests in Techstream would be immensely helpful. Otherwise, you’re pretty much shooting in the dark, throwing money and parts at guesses. See here: http://4runnerclub.com/i/4r_files/f...7toyrm/07toypdf/07rmsour/4runnerr/0060028.pdf

Based on what you provided above, I’d check the air intake for leaks, vacuum/evap hoses for leaks, and clean the MAF. I think the MAF readings you have at 2k RPMs are supposed to be lower (0.71-1.0 lb/min) and at idle are supposed to be lower (0.18-0.3 lb/min).
Why is it on here so many get the code, and then start throwing parts at it?

Friends, family, countrymen, the code doesn't necessarily point to the defective part. Once you get your fault code, google it, and you will see it actually points you down a diagnostic trail. It's the trail head marker. A google search for the P0171 code gave me the following:

P0171 Possible Causes
What does this mean?

Intake air leaks
Faulty front heated oxygen sensor
Ignition misfiring
Faulty fuel injectors
Exhaust gas leaks
Incorrect fuel pressure
Lack of fuel
Faulty Mass Air Flow (MAF) sensor
Incorrect Positive Crankcase Ventilation (PCV) hose connection


This is where you begin, and I do not recommend wasting money on replacing parts hoping you guess correctly. It can add up very quickly. If you lack the skills to diagnose it yourself then your money will be better spent paying for a tech to diagnose it for you for a small fee. You then can decide to fix it yourself or have them do it.
 
I'd start with a reset and a new gas cap. Every 100 out there needs a new one if they haven't yet. Seal no longer a gasket but a piece of non supple plastic, given the age.
 
I'd start with a reset and a new gas cap. Every 100 out there needs a new one if they haven't yet. Seal no longer a gasket but a piece of non supple plastic, given the age.
Thanks for the idea. But mine was replaced 6 months ago.
 
I have found the problem. Looks like my mechanic tried to glue it last time but it did not hold. I have uploaded a few photos. I am now trying to figure out how I am going to attach it because the box it connects to seems to be damaged a little bit.

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I believe that box is polypropylene with ~30% glass fiber. So if you know someone with a hot air welder, you should be able to weld it with some poly rod too, if you prefer to go that route.
Sounds fancy but cool.
 
Haha, I am very fancy indeed. But really, you can pick up a plastic welder for pretty cheap at HF, and most plastic stuff has the type of plastic (PP GF30 in this case) somewhere in the molding. You can just Google the abbreviation for the plastic type and see if it's weldable.
I had no idea about this. So the plastic type (e.g., PP GF30) is typically stamped into the item? I'm a dumbass and never knew that's what those abbreviations were. Looks like $60 at HF can get me going; I assume I only need an air compressor and 120 hook-up to make it work? I want to try this. I break plastic stuff more than I care to admit, which usually gets redneck JB Weld treatment that is more often than not ephemeral.
 
I had no idea about this. So the plastic type (e.g., PP GF30) is typically stamped into the item? I'm a dumbass and never knew that's what those abbreviations were. Looks like $60 at HF can get me going; I assume I only need an air compressor and 120 hook-up to make it work? I want to try this. I break plastic stuff more than I care to admit, which usually gets redneck JB Weld treatment that is more often than not ephemeral.
It's really minimal air flow that's needed, and the $70 dollar one has a fan built in and just needs an outlet. Yeah, most plastic molded stuff has it in the casting. Definitely worth looking into. Things that are impregnated with chemicals tend to not weld well. Check out AVE on Youtube for some insight into various plastics used in tools etc, and how to identify them if they're not marked. (smell, melting point with soldering iron, etc)
 
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