Car AFR's way off, possible O2 issue?
10-18-2015, 12:23 PM
#1
Car AFR's way off, possible O2 issue? *****ISSUE RESOLVED******
The cause of the bogging was both narrowband o2's failing. The cause of the AFR being inconsistent and not hitting stoich (14.7) was due to a faulty wideband sensor. Once these sensors were replaced the car was great.
Read below for symptoms to possibly help yourself, future person reading this.
Stock fuel system. SD tune. No cats, 2 narrowband o2's and 1 wideband o2.
No SES light.
I seafoamed my car via brake booster vacuum port in manifold. We don't need to discuss the intelligence of this decision in this thread. The point is, it was done and now I need to fix the issues it caused (maybe).
See the videos attached for what is happening. The car will warm up idling with AFR's being correct (fairly rich). After it transitions to closed loop it will attempt to maintain stoich (as it should). But instead of bouncing from 14.3-15.1, it will almost rhythmically bounce up to 16-17. It does this when driving also, not just idling.
WOT fuel is way rich. If I continue normal driving the afr will drop into the 10's at idle and begin to run rough.
I pulled out the 2 nb's and 1 wideband and cleaned them with carb cleaner and an air gun. No change.
Using Hp tuners, the Narrowbands seem to be functioning, but it appears that the fuel additions/subtractions are not happening on time. Watch the video to see what I'm talking about; I remember the transition from lean to rich would oscillate more smoothly and predictably.
Hit me with some ideas here fellas.
The cause of the bogging was both narrowband o2's failing. The cause of the AFR being inconsistent and not hitting stoich (14.7) was due to a faulty wideband sensor. Once these sensors were replaced the car was great.
Read below for symptoms to possibly help yourself, future person reading this.
Stock fuel system. SD tune. No cats, 2 narrowband o2's and 1 wideband o2.
No SES light.
I seafoamed my car via brake booster vacuum port in manifold. We don't need to discuss the intelligence of this decision in this thread. The point is, it was done and now I need to fix the issues it caused (maybe).
See the videos attached for what is happening. The car will warm up idling with AFR's being correct (fairly rich). After it transitions to closed loop it will attempt to maintain stoich (as it should). But instead of bouncing from 14.3-15.1, it will almost rhythmically bounce up to 16-17. It does this when driving also, not just idling.
WOT fuel is way rich. If I continue normal driving the afr will drop into the 10's at idle and begin to run rough.
I pulled out the 2 nb's and 1 wideband and cleaned them with carb cleaner and an air gun. No change.
Using Hp tuners, the Narrowbands seem to be functioning, but it appears that the fuel additions/subtractions are not happening on time. Watch the video to see what I'm talking about; I remember the transition from lean to rich would oscillate more smoothly and predictably.
Hit me with some ideas here fellas.
Last edited by jbrockwell; 10-23-2015 at 02:36 PM. Reason: resolved
10-18-2015, 09:45 PM
#2
Update:
I pulled both O2's out to bench test them.
My procedure was heating the tip of them with a propane torch and watching the voltage reading go to ~900mV then removing the flame and watching the voltage immediately go to ~100mV or less.
Bank 1 worked correctly while bank 2 climbed to around 500mV and stayed there, even after the flame was removed. I put bank 1 sensor back in and a replacement for bank 2 (used, but tested correctly).
After the car started the AFR sat at around 13:1 according to the wideband. The readings in Hptuners were Bank 1--> ~890mV and Bank 2--> ~450mV.
These readings did not change as it sat there, so I shut it down. Then, with the car off, the readings were Bank 1--> ~100mV and Bank 2--> ~450mV.
So the value for bank 2 never changed almost as if it was not working correctly, and the car was not entering closed loop.
I tested the original bank 2 sensor again and it passed this time. Keep in mind it failed my first test. I reinstalled it, and stated the car again. Now the car entered open loop and had the same exact issue as in the original post.
I have absolutely no idea what to make of this. My only idea is that the sensors are working but sluggish. I still don't have an explanation for why the sensor froze at 450mV after passing bench but I will try to get 2 new sensors tomorrow.
I pulled both O2's out to bench test them.
My procedure was heating the tip of them with a propane torch and watching the voltage reading go to ~900mV then removing the flame and watching the voltage immediately go to ~100mV or less.
Bank 1 worked correctly while bank 2 climbed to around 500mV and stayed there, even after the flame was removed. I put bank 1 sensor back in and a replacement for bank 2 (used, but tested correctly).
After the car started the AFR sat at around 13:1 according to the wideband. The readings in Hptuners were Bank 1--> ~890mV and Bank 2--> ~450mV.
These readings did not change as it sat there, so I shut it down. Then, with the car off, the readings were Bank 1--> ~100mV and Bank 2--> ~450mV.
So the value for bank 2 never changed almost as if it was not working correctly, and the car was not entering closed loop.
I tested the original bank 2 sensor again and it passed this time. Keep in mind it failed my first test. I reinstalled it, and stated the car again. Now the car entered open loop and had the same exact issue as in the original post.
I have absolutely no idea what to make of this. My only idea is that the sensors are working but sluggish. I still don't have an explanation for why the sensor froze at 450mV after passing bench but I will try to get 2 new sensors tomorrow.
Last edited by jbrockwell; 10-18-2015 at 09:58 PM.
10-20-2015, 01:50 PM
#4
Around 13:1 at idle and shoots way lean under load. I attributed this to it being tuned in 80* weather, and it was around 40* when that was tested.
I installed new O2's today and drove for a while. The AFR's still a bit off but this could be due to a combination of new sensors and the temperature change outside. However, it did not start to bog and run pig rich this time so I believe the new sensors helped.
I'm going to attempt to tune it to this weather later tonight and see what happens.
I installed new O2's today and drove for a while. The AFR's still a bit off but this could be due to a combination of new sensors and the temperature change outside. However, it did not start to bog and run pig rich this time so I believe the new sensors helped.
I'm going to attempt to tune it to this weather later tonight and see what happens.
Last edited by jbrockwell; 10-20-2015 at 03:51 PM.
10-21-2015, 05:42 PM
#5
New sensors are in. The car does not bog and run rich after a while now, but the afr still bounces around quite a bit. I made a log of the narrowband reading vs the wideband reading at idle. My initial thoughts today were that the sensor is not switching quick enough but after looking at various other logs I talked myself out of that.
All injectors are vibrating, bank 1 and 2 fuel trims are the same, and no vacuum leaks to be found.
The search continues.
All injectors are vibrating, bank 1 and 2 fuel trims are the same, and no vacuum leaks to be found.
The search continues.
