To be clear (in my mind anyway), you swapped the upstream A/F sensors as opposed to the downstream O2 sensors, correct?
P0174, Rough Idle & Strong Exhaust Smell
- Thread starter BoostinZX
- Start date
To be clear (in my mind anyway), you swapped the upstream A/F sensors as opposed to the downstream O2 sensors, correct?
BoostinZX
New member
Yes, the front A/F sensors (upstream) are the ones that i swapped. And after swapping them, the problem moved to the other side (from Bank 2 to Bank 1) i now am getting a P0171 instead of the P0174 as before. The Short Term Fuel Trim issue also moved sides when i moved the sensor over. So that definitely showed me where the issue was.
I took the sensor and it was still under warranty to the local advance auto parts and they swapped it out. I installed the new sensor and all has been well for 2 days now.
If you are experiencing a similar issue, i wouldn't immediately jump to a bad A/F sensor (especially since i replaced mine less than a year ago and it apparently failed in that amount of time) but it wouldn't hurt to swap them and see if your issue changes sides. I would definitely still try and look for any vacuum leaks, etc. as well... I would highly recommend to buy the android app Torque Pro and a OBDII scanner that talks to it. That was a very nice tool to have during this process. I would have still been able to find the issue eventually i think because i had a normal scanner that would show me the codes, but actually seeing the short term fuel trim issues move sides as well was an extra check toward it being the A/F sensor.
I'm still not 100% sure that its the root of all the problems, there may be something else underlying that's causing the sensor to go bad? but only time will tell now that i have a new one installed.
Hope that some of my info has helped! And good luck with tracking yours down!
I took the sensor and it was still under warranty to the local advance auto parts and they swapped it out. I installed the new sensor and all has been well for 2 days now.
If you are experiencing a similar issue, i wouldn't immediately jump to a bad A/F sensor (especially since i replaced mine less than a year ago and it apparently failed in that amount of time) but it wouldn't hurt to swap them and see if your issue changes sides. I would definitely still try and look for any vacuum leaks, etc. as well... I would highly recommend to buy the android app Torque Pro and a OBDII scanner that talks to it. That was a very nice tool to have during this process. I would have still been able to find the issue eventually i think because i had a normal scanner that would show me the codes, but actually seeing the short term fuel trim issues move sides as well was an extra check toward it being the A/F sensor.
I'm still not 100% sure that its the root of all the problems, there may be something else underlying that's causing the sensor to go bad? but only time will tell now that i have a new one installed.
Hope that some of my info has helped! And good luck with tracking yours down!
BoostinZX , i have the same identical problem as you with the P0174 code and the list of symptom that you have. In addition, i also have code P0430 but it might go away once i fix the P0174 (i hope). I had this for a few months now and I just ignored it for a while. I have a 2004 V6 1GR-FE engine. This one stated as system too lean.
Anyway, what AF sensor (and part #) should i replace? Is this the one on the driver side or passenger side? I found a couple on Amazon's site but i don't know which one to buy.
Does anyone have a PDF on where these sensors are located?
Downstream Right
https://www.amazon.com/Denso-234-48...0013TOW9W/ref=cm_cr_arp_d_product_top?ie=UTF8
Downstream Left
https://www.amazon.com/dp/B0013TQRL...TF8&colid=1KWEKZFNM7QSL&coliid=I2LTY40FY39XFH
A more expensive one is also listed.
https://www.amazon.com/Denso-234-90...004:toyota:4runner&keywords=4runner+o2+sensor
Anyway, what AF sensor (and part #) should i replace? Is this the one on the driver side or passenger side? I found a couple on Amazon's site but i don't know which one to buy.
Does anyone have a PDF on where these sensors are located?
Downstream Right
https://www.amazon.com/Denso-234-48...0013TOW9W/ref=cm_cr_arp_d_product_top?ie=UTF8
Downstream Left
https://www.amazon.com/dp/B0013TQRL...TF8&colid=1KWEKZFNM7QSL&coliid=I2LTY40FY39XFH
A more expensive one is also listed.
https://www.amazon.com/Denso-234-90...004:toyota:4runner&keywords=4runner+o2+sensor
Last edited:
BoostinZX
New member
I am bringing this thread back from the dead... I had another one of the front Air/Fuel sensors fail on me again... causing a similar, but different condition... I'm not 100% sure that the problem is fixed at this point, but it seems to be intermittent or fixed.
I am now getting a P0172 & P0175, and the truck is running very rich smelling out the exhaust... Looking at the Torque Pro app, its pulling up to -40% on both banks trying to compensate... Not sure what is causing the issue on both banks, but I have cleaned the MAF (even though i replaced back when i was having these other issues) and checked for Vacuum leaks again.
I went ahead and bit the bullet and replaced both front Air/Fuel sensors... and the problem went away for 2 days... Then it sort of came back and ran like crap for a day... and now its been running great for the past 4 days...
Just wanted to update this thread to see if anyone else has had these types of issues, and if so, what was your final fix? I feel like the Air/Fuel sensors may only be "patching" the true problem at this point...
I am now getting a P0172 & P0175, and the truck is running very rich smelling out the exhaust... Looking at the Torque Pro app, its pulling up to -40% on both banks trying to compensate... Not sure what is causing the issue on both banks, but I have cleaned the MAF (even though i replaced back when i was having these other issues) and checked for Vacuum leaks again.
I went ahead and bit the bullet and replaced both front Air/Fuel sensors... and the problem went away for 2 days... Then it sort of came back and ran like crap for a day... and now its been running great for the past 4 days...
Just wanted to update this thread to see if anyone else has had these types of issues, and if so, what was your final fix? I feel like the Air/Fuel sensors may only be "patching" the true problem at this point...
BoostinZX, i am glad you are reviving this thread as i have the similar issue still at this time. How many miles do you have on your truck? Mine was the occasion alternating P0174 and P0430 code and my current fix is to use my code reader to reset it. (had replaced one of the O2 sensors too and did nothing). It would usually go away for a tank or two before it comes back. The car sometimes would idle a bit rough (hovering around 600-700rpm) when cold in a stop light. it never stalls.
Let me know if you have fixed your issue by replacing the two AF sensors. I know one of the sensors cost 3x as much as the O2 sensor.
I have around 187,000 miles on the odometer now. Other than that, car runs fine. I used it for a 3 hour trip recently and the MPG is holding steady at around 18-19.5MPG.
Let me know if you have fixed your issue by replacing the two AF sensors. I know one of the sensors cost 3x as much as the O2 sensor.
I have around 187,000 miles on the odometer now. Other than that, car runs fine. I used it for a 3 hour trip recently and the MPG is holding steady at around 18-19.5MPG.
BoostinZX
New member
PTPT2002, my 4Runner currently has 173k on it. Mine is also a V8, so not sure that makes a difference with the issues or possible fixes. So far, the codes have not come back or the roughness that I experienced out of the blue after I swapped the 2 front Air/Fuel sensors again. I think it may have remedied the problem, or at least masked it for now again. I will keep you posted, but if anyone else would like to chime in, the more the merrier 
Also, if you have an android tablet or phone, and can spend the $, its a great investment to get a bluetooth OBDII scanner and the Torque Pro app from the android market. It is how I noticed that my fuel trims were way off when I was originally having issues and helped me troubleshoot from there. I would see if one bank is reading +-20% or more and that would be the first Air/Fuel sensor that I would swap instead of replacing both at the same time, unless you just feel like doing them both at the same time.
Also, if you have an android tablet or phone, and can spend the $, its a great investment to get a bluetooth OBDII scanner and the Torque Pro app from the android market. It is how I noticed that my fuel trims were way off when I was originally having issues and helped me troubleshoot from there. I would see if one bank is reading +-20% or more and that would be the first Air/Fuel sensor that I would swap instead of replacing both at the same time, unless you just feel like doing them both at the same time.
BoostinZX
New member
Raygenjay do you know of any way to test this at home? Or would this be something I could request to be checked at a dealer? I borrowed a fancy scanner from a friend, but all the digging around I did, I couldn't find anything for injector duty or anything like that. I could increase/decrease the percentage that the injector was flowing, but the ECU would just compensate.
The car runs great at WOT. And has been running great since last Tuesday, but your theory has me intrigued
If there is no way to "test" easily while running. Maybe I can pull them all and have them flow tested to see if they are functional. Then that would hopefully determine if one is stuck correct?
Sent from my iPhone using Tapatalk
The car runs great at WOT. And has been running great since last Tuesday, but your theory has me intrigued
If there is no way to "test" easily while running. Maybe I can pull them all and have them flow tested to see if they are functional. Then that would hopefully determine if one is stuck correct?
Sent from my iPhone using Tapatalk
Have you tried replacing the maf? That could affect both sets of cylinders at once and combined with a bad o2 Sensor could explain some of your issues. Injectors can be sent out for a sonic cleaning, there are several companies that do this, also my truck previous owner had an injector cleaning service preformed at the dealer several times prior to my buying it ( listed on receipts) not sure what this entails but it might be worth your looking into.
BoostinZX
New member
I have replaced the MAF 2 times during the entirety of the troubleshooting. I think I am definitely going to look into the injectors next. More in new post below....
BoostinZX
New member
So another update, and bringing back from the dead...
After the problem arose yet again, I went out, bought 2 new front Air/Fuel sensors and swapped them out...
Problem was fixed yet again... or was it...
Fast forward 4 more months, and its doing the exact same thing again... So clearly the front Air/Fuel sensors are fixing the problem, but that fix is just masking the larger issue that I have not been able to source yet.
My next course of action is to remove and inspect the injectors myself, and then likely have them cleaned/flow/leak tested or replace with new. I would like to have the old ones at least looked at so I can hopefully determine if that was the ultimate root to all of the issues in the first place.
If the injectors do not fix the issue, then i would be leaning toward fuel pump and may try that next... After that, I am grasping at straws again... Just wanted everyone that was following to have an update that its not fixed, that my "fix" was just masking whatever the true issue is and was getting me by for a few months trouble free.
I will keep you posted, but if anyone else has anything to add, please do so!
After the problem arose yet again, I went out, bought 2 new front Air/Fuel sensors and swapped them out...
Problem was fixed yet again... or was it...
Fast forward 4 more months, and its doing the exact same thing again... So clearly the front Air/Fuel sensors are fixing the problem, but that fix is just masking the larger issue that I have not been able to source yet.
My next course of action is to remove and inspect the injectors myself, and then likely have them cleaned/flow/leak tested or replace with new. I would like to have the old ones at least looked at so I can hopefully determine if that was the ultimate root to all of the issues in the first place.
If the injectors do not fix the issue, then i would be leaning toward fuel pump and may try that next... After that, I am grasping at straws again... Just wanted everyone that was following to have an update that its not fixed, that my "fix" was just masking whatever the true issue is and was getting me by for a few months trouble free.
I will keep you posted, but if anyone else has anything to add, please do so!
I've had the same symptoms in my '08 V6 4Runner. Persistent p0174 and p2197 codes after replacing the MAF, AF/O2 sensors, spark plugs, gas cap, and most recently replaced fuel injectors on bank 2. After the fuel injector swap it ran really well for about 25 miles, then threw the codes again. Replaced the AF/O2 sensor on bank 2 (upstream) again and it went well for another 150 miles, and now it's back to doing the same thing: idling rough, rich exhaust smell, etc. I'm not sure what I'm going to try next as the injectors didn't fix it either. OP: If yours gets better after doing the injectors I'd love to know about it. Or if anyone has any other ideas. I'm kinda stumped by this and I'm tired of throwing money away on repairs that don't fix it. I'm actually wondering if the ECM might be bad (rare as that would be). But I had the ECM re-flashed a year ago already, again without any fix. My trusty mechanic and the dealership are equally clueless on this one. Anyone out there have any thoughts on what to try next? Frustrated :frusty:
Last edited:
So another update, and bringing back from the dead...
After the problem arose yet again, I went out, bought 2 new front Air/Fuel sensors and swapped them out...
Problem was fixed yet again... or was it...
Fast forward 4 more months, and its doing the exact same thing again... So clearly the front Air/Fuel sensors are fixing the problem, but that fix is just masking the larger issue that I have not been able to source yet.
My next course of action is to remove and inspect the injectors myself, and then likely have them cleaned/flow/leak tested or replace with new. I would like to have the old ones at least looked at so I can hopefully determine if that was the ultimate root to all of the issues in the first place.
If the injectors do not fix the issue, then i would be leaning toward fuel pump and may try that next... After that, I am grasping at straws again... Just wanted everyone that was following to have an update that its not fixed, that my "fix" was just masking whatever the true issue is and was getting me by for a few months trouble free.
I will keep you posted, but if anyone else has anything to add, please do so!
well i have read, that if you have a leaking injector, it "can" cause the sensors to go bad, because its burning raw fuel in the headers, instead of the cylinders.
also, injectors can bench test good, but still leak, so the only way to know for sure if it leaks is, use a camera bore scope into the spark plug hole, soon after turning engine off, if its going to leak, it will be easiest to see, within the first few minutes, while the pressure in the system is highest
just FYI
on a side note, did you ever check to see if the cats were restricted? if so they could be scrambling the whole fuel air o2 sendor readings to ecm juggling act
Last edited:
BoostinZX
New member
Thank you for the info keakar. I am definitely still leaning towards the injectors... What makes it even more weird is the fact that its so intermittent. The issue happened the other day when i updated this post, and now the truck has been running great the past 2 days. I also put a fuel pressure gauge on it again last night just to keep track of it... If it is a failing injector, then its intermittently failing and not completely failed and stuck open. Right now with the truck running good, fuel pressure holds at 40psi, and 30 minutes after shutting the truck off, it had only dropped to 30psi. That makes me think that the regulator/pump/etc. are all good.
I will keep you guys posted, but may try to replace the injectors next... I hate to keep throwing money at it, but i don't feel comfortable taking it to someone that won't automatically blame the secondary air bypass once they see it.
As for the cats, I have not had those checked, temps seem fine though on both banks for them, and we had them replaced under a TSB (strong rotten egg smell) about 4 years and 80k ago? May have to get those looked at as well just to rule them out.
Thanks again for all the suggestions and keep them coming!
I've got a p0174 code coming up as well. Along with this I've got p0136. The p0136 has been on and off for about a year. I replaced both downstream sensors, and the code still comes back.
Since the p0174 started, I've been noticing a slight miss at stoplights. This mainly happens right after getting gas. The gas cap has been replaced within the past few years. Next step is to check the plugs and clean the maf.
Since the p0174 started, I've been noticing a slight miss at stoplights. This mainly happens right after getting gas. The gas cap has been replaced within the past few years. Next step is to check the plugs and clean the maf.
BoostinZX
New member
So another update...
I've had the fuel pressure gauge hooked up for a few weeks now. Even swapped with a different one to make sure my findings weren't related to the gauge itself...
1. When turning on the ignition (but not starting the car) I have 0psi at the fuel rail testing port. Once I start the car, it takes about 3-4 seconds, but it immediately goes up to 41psi and holds there perfectly until i turn the car of still... I'm not sure if the car should have pressure with the key turned on, or if the fuel pump only starts pushing fuel once the vehicle ignition has been triggered? If anyone can chime in here on if this is normal, that would be awesome!
The car has been running great up until 2 days ago... Started running rough and hesitant at takeoff, etc... idling very rough at stoplights... and finally the check engine light kicked on and the fuel trims on bank2 got very saturated again...
My Torque Pro catalyst temperatures were identical on both sides (not sure how accurate that is) but i'm assuming its not a clogged cat still...
I'm still leaning toward a faulty or multiple intermittently faulty injectors. I am going to purchase new ones in the near future and then send mine off to have them flow/leak tested to see if one was perhaps the culprit...
Any other suggestions? and I will keep you posted on progress if any... seems so weird how intermittent the issue is, and i can't pinpoint it to 1 specific scenario (temp, just after car wash, fuel level, driving conditions, etc.)...
As always, ideas are welcome
I've had the fuel pressure gauge hooked up for a few weeks now. Even swapped with a different one to make sure my findings weren't related to the gauge itself...
1. When turning on the ignition (but not starting the car) I have 0psi at the fuel rail testing port. Once I start the car, it takes about 3-4 seconds, but it immediately goes up to 41psi and holds there perfectly until i turn the car of still... I'm not sure if the car should have pressure with the key turned on, or if the fuel pump only starts pushing fuel once the vehicle ignition has been triggered? If anyone can chime in here on if this is normal, that would be awesome!
The car has been running great up until 2 days ago... Started running rough and hesitant at takeoff, etc... idling very rough at stoplights... and finally the check engine light kicked on and the fuel trims on bank2 got very saturated again...
My Torque Pro catalyst temperatures were identical on both sides (not sure how accurate that is) but i'm assuming its not a clogged cat still...
I'm still leaning toward a faulty or multiple intermittently faulty injectors. I am going to purchase new ones in the near future and then send mine off to have them flow/leak tested to see if one was perhaps the culprit...
Any other suggestions? and I will keep you posted on progress if any... seems so weird how intermittent the issue is, and i can't pinpoint it to 1 specific scenario (temp, just after car wash, fuel level, driving conditions, etc.)...
As always, ideas are welcome
Streetfighter
New member
dude, have you checked the timing?
Your timing jumped!
it will take 30 mins to check.
Your timing jumped!
it will take 30 mins to check.
So another update...
I've had the fuel pressure gauge hooked up for a few weeks now. Even swapped with a different one to make sure my findings weren't related to the gauge itself...
1. When turning on the ignition (but not starting the car) I have 0psi at the fuel rail testing port. Once I start the car, it takes about 3-4 seconds, but it immediately goes up to 41psi and holds there perfectly until i turn the car of still... I'm not sure if the car should have pressure with the key turned on, or if the fuel pump only starts pushing fuel once the vehicle ignition has been triggered? If anyone can chime in here on if this is normal, that would be awesome!
The car has been running great up until 2 days ago... Started running rough and hesitant at takeoff, etc... idling very rough at stoplights... and finally the check engine light kicked on and the fuel trims on bank2 got very saturated again...
My Torque Pro catalyst temperatures were identical on both sides (not sure how accurate that is) but i'm assuming its not a clogged cat still...
I'm still leaning toward a faulty or multiple intermittently faulty injectors. I am going to purchase new ones in the near future and then send mine off to have them flow/leak tested to see if one was perhaps the culprit...
Any other suggestions? and I will keep you posted on progress if any... seems so weird how intermittent the issue is, and i can't pinpoint it to 1 specific scenario (temp, just after car wash, fuel level, driving conditions, etc.)...
As always, ideas are welcome
Have you ever used Seafoam? When added to gas, it cleans injectors. Might be worth a shot.
Streetfighter
New member
This exact same thing happened to me.
Went from running like a sewing machine to idling like a washing machine filled with wool blankets.
I thought it was plugs, coils, fuel delivery, sensors etc.
at the end, the timing jumped.
How old is your timing belt? if the tensioner goes after time, it could jump which will cause that radom terrible shaking idle.
happened to me on this post.
http://www.toyota-4runner.org/4th-g...-fe-timing-belt-failure-aftermath-repair.html
Went from running like a sewing machine to idling like a washing machine filled with wool blankets.
I thought it was plugs, coils, fuel delivery, sensors etc.
at the end, the timing jumped.
How old is your timing belt? if the tensioner goes after time, it could jump which will cause that radom terrible shaking idle.
happened to me on this post.
http://www.toyota-4runner.org/4th-g...-fe-timing-belt-failure-aftermath-repair.html
Similar threads
