Why do my O2s keep flatlining?
Why do my O2s keep flatlining? Ive been trying to figure this out for months now and I think my overly rich situations are caused clearly because of this problem. Here is a picture of my chart that shows this happening when Im not even on the gas and just about deceling
So as you can see when it flatlines, my Trims go way south. Im running 30lb SVOs now. Had 60lbs in there and took them out.
Are these O2s pretty much dying? Some say I need to adjust the switching, I have absoluetely no clue on how to set those values, there really doesnt seem to be any good threads on how to do this accurately.
Dixit
So as you can see when it flatlines, my Trims go way south. Im running 30lb SVOs now. Had 60lbs in there and took them out.
Are these O2s pretty much dying? Some say I need to adjust the switching, I have absoluetely no clue on how to set those values, there really doesnt seem to be any good threads on how to do this accurately.
Dixit
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Joined: Mar 2003
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People with Kooks usually have good/sharp O2 switching; at least from the two I have seen. If this is something that has just started I would say the sensors are headed out, but strange they would both go 
Several members have recommended I adjust the switching values also OR there is the proportional fueling nightmare you can try. BTW mine do almost the same thing, but once I get back on the throttle they start switching again, although very slow (good ole LGs!!!)
Several members have recommended I adjust the switching values also OR there is the proportional fueling nightmare you can try. BTW mine do almost the same thing, but once I get back on the throttle they start switching again, although very slow (good ole LGs!!!) I'm working through the same issue on my C5. While I don't have an absolute solution, I can tell you some things that make it better.
When I started, my AFR (measured via wideband) at idle was around 11.x-12.x with a commanded AFR of 14.6. From looking at your chart your TPS sits at 7% at idle, same as mine. I went into the Open/Closed loop screen and set my Idle TPS threshold to 8% to ensure the idle table would be used during idle instead of the closed loop proportional table. I set the base adder in the airflow table to between 10-25 in the first three cells.
In the General Fuel tab I scaled the min. inj. pulse by -10%. This change perked up my O2s and got them swinging at idle. Running bigger injectors with the same min pulse, I believe adds too much fuel and makes the O2s hang.
Right now they are still kinda jagged (instead of nice and round) but the commanded AFR vs. actual is pretty much dead on. I've got some more fine tuning to do, but I think I'm on the right track.
When I started, my AFR (measured via wideband) at idle was around 11.x-12.x with a commanded AFR of 14.6. From looking at your chart your TPS sits at 7% at idle, same as mine. I went into the Open/Closed loop screen and set my Idle TPS threshold to 8% to ensure the idle table would be used during idle instead of the closed loop proportional table. I set the base adder in the airflow table to between 10-25 in the first three cells.
In the General Fuel tab I scaled the min. inj. pulse by -10%. This change perked up my O2s and got them swinging at idle. Running bigger injectors with the same min pulse, I believe adds too much fuel and makes the O2s hang.
Right now they are still kinda jagged (instead of nice and round) but the commanded AFR vs. actual is pretty much dead on. I've got some more fine tuning to do, but I think I'm on the right track.
Muncie21, thanks for the info. Im going to change the TPS threshold to 8 and see how that works. However, the options you mentioned about base adder in the airflow table, I dont see that.
Dixit
Dixit
Originally Posted by Dixit
However, the options you mentioned about base adder in the airflow table, I dont see that.
Dixit
Dixit
I have Closed Loop Proportional/Airflow mode and Closed Loop Proportional IDLE/Airflow. Both the Airflow Mode and Airflow tables contain settings for Base Addr vs. Airflow mode.
I believe the Proportional Idle table is selected when the Proportional Idle Thresholds conditions are met. Since I idle at 7%, I increased the Idle TPS threshold to 8% to ensure that changes I made to the idle airflow table were used at idle instead of the Airflow mode table.
Well I set the TPS to 9% and now at Idle its really bad trim wise and O2 wise. It basically stays flatline until the LTFTs and STFTs pull back big time, almost like 25% between the two. Then the O2s start switching again. Also driving, everytime I press the clutch and obviously im off the gas and its below the 9%, the O2s are straight flat and the trims are trying to pull back a good 25-30% combined. So its running crazy rich now on the closed throttle. Now sure why, what dont make sense is that idle setup only kicks in if its below 9% and below 15mph. Even if Im at 50mph and I press the clutch in to coast to a stop, the O2s are flat and LTFT+STFT is sitting at -35% combined. So that one single change I made dont make sense since at 50mph it shouldnt be affected.
Going to have to look more into this and figure out wtf just went wrong.
Dixit
Going to have to look more into this and figure out wtf just went wrong.
Dixit
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After re-reading the help on HPtuners, I think I found the problem. 9% is way too high. Whats wierd is that the help is contradicting on Ver 2.1 HPTuners.
When you are editing the variable, the bottom that shows the help of that variable says "Throttle positing must be below this value to enable idle proportional closed loop fueling tables"
But if you go to the help itself it says the following for the same variable "Minimum Throttle Position Percent Required"
So if I go by the Help itself, that means I basically just disabled it because at 9% my TPS never is at 9% minimum when the idle proportional kick is. Where it was before at 5% it kicked in because it was higher than 5%. It seems this table is not used at Idle/0mph situations since the 15mph threshold is not met either.
But that still dont explain why my O2s slightly flatline when I get off the gas before I made these changes. This is definetely causing my car to run rich when it flatlines as the trims keep pushing negative to pull back the fuel.
Dixit
When you are editing the variable, the bottom that shows the help of that variable says "Throttle positing must be below this value to enable idle proportional closed loop fueling tables"
But if you go to the help itself it says the following for the same variable "Minimum Throttle Position Percent Required"
So if I go by the Help itself, that means I basically just disabled it because at 9% my TPS never is at 9% minimum when the idle proportional kick is. Where it was before at 5% it kicked in because it was higher than 5%. It seems this table is not used at Idle/0mph situations since the 15mph threshold is not met either.
But that still dont explain why my O2s slightly flatline when I get off the gas before I made these changes. This is definetely causing my car to run rich when it flatlines as the trims keep pushing negative to pull back the fuel.
Dixit
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Verdad Gallardo You might want to zero out the first three cells (low load) in one of the tables so you can figure out which one is controlling the fuel. Either that, or just copy one to the other and make the same changes to both.
Obviously you are adding too much fuel. For the proportional table to work your fueling has to be close to right. Doublecheck your IFR table, as this is the basis for all fueling. If you are confident the IFR is right, I would look at the avg inj. pulse width at idle and compare to min. pulse width table. If they are close, take out a % from the min. pulse width table.
Finally, I'd suggest doing idle tuning without driving and getting the O2s moving correctly there first. This way you don't have to worry about DFCO interferring (or not) and other things. Ok, one more thing. Log your FTCs as I've seen a slight difference between cell 20 and 19.
Obviously you are adding too much fuel. For the proportional table to work your fueling has to be close to right. Doublecheck your IFR table, as this is the basis for all fueling. If you are confident the IFR is right, I would look at the avg inj. pulse width at idle and compare to min. pulse width table. If they are close, take out a % from the min. pulse width table.
Finally, I'd suggest doing idle tuning without driving and getting the O2s moving correctly there first. This way you don't have to worry about DFCO interferring (or not) and other things. Ok, one more thing. Log your FTCs as I've seen a slight difference between cell 20 and 19.
Originally Posted by Billiumss
I noticed mine was doing that the other day, any real fix for this to make them switch faster? Mine does it mostly at idle.
Bill
Bill
Originally Posted by Billiumss
Yep, I have SVO 30lbs in there, what should it be set at?
I let mine idle for about 1.5 minutes to make sure the O2s are swinging good, cause on start up it (my car) uses FTC 20 and after 1min40sec it goes to FTC19 and stays there the rest of the time.
Ive taken out 30% from my min pulse width table and still same problem. Im running the SVO30s as well.
Ive noticed that in SDmode it is not as bad as it is in MAF mode. In MAF mode the O2s rails for a much longer time.
Dixit
Ive noticed that in SDmode it is not as bad as it is in MAF mode. In MAF mode the O2s rails for a much longer time.
Dixit
Originally Posted by Billiumss
Take out from where? IFR table is correct. I am in FTC 19 at idle.
You need to make sure your VE is correct before you start messing with fueling. Just my $.02 worth.
Originally Posted by Dixit
Ive taken out 30% from my min pulse width table and still same problem. Im running the SVO30s as well.
Ive noticed that in SDmode it is not as bad as it is in MAF mode. In MAF mode the O2s rails for a much longer time.
Dixit
Ive noticed that in SDmode it is not as bad as it is in MAF mode. In MAF mode the O2s rails for a much longer time.
Dixit
Is your issue flat O2s at idle or during decel?
Originally Posted by muncie21
If you've put in bigger injectors and haven't decreased you min inj. pulse, you could be shooting in too much fuel at idle. Other place to look is proportional gain at idle.