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Hello do you think my problem could come from a oxygen sensor?
after many test with vcdm a 1 oxygen sensor after turbo give very low information (1) in bank 2 in contrary with those in bank 1 (2)
Not completely clear of your description. Possibility a clogged catalytic converter. A clogged converter can cause a deviation of the O2 sensors. Causing a performance problem. On vcds, suggest doing a datalog of the O2 sensors.
Last edited by 1eapplebaum; Jul 26, 2019 at 05:05 PM.
I too don't understand the issue with such vague description. I agree that one test I would do is a DL of fuel trims. It will not necessarily point directly to a failure, but at least it can reduce the options
Operating correctly (efficiently) O2 sensors swing within a voltage range based on the amount of unburned fuel left in the exhaust. It is normal they swing high, low, back to high in a pattern that resembles a sine wave. Not actually a sine wave though. O2 sensors are rudimentary widebands. They are incapable of any specific AFR reading, instead, they signal to the ECU that fueling is rich, or lean, or really rich, or really lean. Based on the mv received from the O2, the ECU adjusts fueling
O2 sensors can fail in several ways. They can get lazy, unable to switch fast enough to keep up with combustion cycles. They can lose their voltage range (high and low,; or high or low). They can fail completely. So, although a DL will not necessarily point directly to the problem they can at least display the health of the sensors.
Here is a DL I did recently on an SC engine that I tuned. The leftside/rightside O2 voltage signals are shown in the 4th window row (in light/dark blues). In this window, everything from left to the rightside where the vertical white bar is shows fairly healthy O2 sensors, switching the way they should. At the moment just left of the vertical line, Closed loop went open and changed to power enrichment. O2 sensors flatline in PE and fueling is done strictly via a PE fueling table along with a multiplier. The top pane shows fueling (done with a real wideband in the exhaust), the low spike right before the vertical shows PE fueling (about 11.75:1 for an FIed engine), then the vertical rests on DFCO (foot removed from accelerator), and jumps approx. to 22:1 which is typical for emissions in any modern EMS.
So, bottom line - look for the wavy lines in closed loop. If you do not have it in both front O2 sensors, then look further into the one not cycling.
I too don't understand the issue with such vague description. I agree that one test I would do is a DL of fuel trims. It will not necessarily point directly to a failure, but at least it can reduce the options
Operating correctly (efficiently) O2 sensors swing within a voltage range based on the amount of unburned fuel left in the exhaust. It is normal they swing high, low, back to high in a pattern that resembles a sine wave. Not actually a sine wave though. O2 sensors are rudimentary widebands. They are incapable of any specific AFR reading, instead, they signal to the ECU that fueling is rich, or lean, or really rich, or really lean. Based on the mv received from the O2, the ECU adjusts fueling
O2 sensors can fail in several ways. They can get lazy, unable to switch fast enough to keep up with combustion cycles. They can lose their voltage range (high and low,; or high or low). They can fail completely. So, although a DL will not necessarily point directly to the problem they can at least display the health of the sensors.
Here is a DL I did recently on an SC engine that I tuned. The leftside/rightside O2 voltage signals are shown in the 4th window row (in light/dark blues). In this window, everything from left to the rightside where the vertical white bar is shows fairly healthy O2 sensors, switching the way they should. At the moment just left of the vertical line, Closed loop went open and changed to power enrichment. O2 sensors flatline in PE and fueling is done strictly via a PE fueling table along with a multiplier. The top pane shows fueling (done with a real wideband in the exhaust), the low spike right before the vertical shows PE fueling (about 11.75:1 for an FIed engine), then the vertical rests on DFCO (foot removed from accelerator), and jumps approx. to 22:1 which is typical for emissions in any modern EMS.
So, bottom line - look for the wavy lines in closed loop. If you do not have it in both front O2 sensors, then look further into the one not cycling.
Wow all credit to you Sir Mr BWings great wright up ...
Hello my friends, thank you for your answers.....
i think i have found my problem.....
see below two pictures, what your opinion??.
Pressure hose, charge air cooler n*17
I went back and reread your posts. I am still not completely clear on the issues you are experiencing. With your most recent post/pictures, if you have ANY air leaks in any of the tubing past the MAF(s), through the intercoolers, it will cause lean fueling conditions. When the ECU senses lean conditions it will set a CEL. Lean is the worse of the two conditions lean or rich. Lean can destroy an engine so the EMS is designed to protect itself. These conditions are exacerbated by heat (and warmer climate conditions).
I also reviewed the post you have that shows the cats and O2 sensors. When I follow your writing, and if I understand the question, it appears you are trying to compare the performance of two O2 sensors that might be in different positions. Think of the O2 sensors as "forward of the cat" and after the Cat. You only want to be interested in the two forward O2 sensors (before the Cats) on bank 1 and compare to same at bank two. Disregard the two after the cats for performance comparisons sake as the fronts do different things than the rears.
Finally, YES, look for any air leaks in any of the airflow tubes.
That probably is not the problem. Re-read BWings explanation.
The Audi group recommends changing both sensors right and left. Possibly, is the other sensor the old style? Not saying this is the problem but worth checking.
Hello thank you for your answer.
both had been chaned last year.
do you think one could already be damage????
Anything is possible but it is not likely. Do you have a continuously lit check engine light or when scaning the car the code comes up. I would suggest checking wiring for broken connections or corrosion as you have been doing.
Use vcds to do a live monitor or data log of the turbo pressure as the RPMs increase. This is the to determinate if the car is going into limp mode to protect the turbos. The other live scan is to monitor the O2 sensors. These two tests will be performed with the laptop hooked up and driving the vehicle through the RPM ranges.
Without this information we are guessing at the problem. Before doing any of this please erase all trouble codes and start fresh.
Last edited by 1eapplebaum; Aug 4, 2019 at 08:27 AM.
At this point I'm not sure. The purpose of the diagnostic check up I suggest is to make sure everything is functioning properly.
My suspicion is somewhere in the electronics is corrosion, causing some of the problems. An example was the two corroded relays. There is something else corroded. We need to verify this otherwise more parts will be replaced needlessly.
The thing which seems to give a bit less is the oxygen sensor, before catalyst 7-12 bank 2, according to mechanic.
They works but they doesn’t appear Fault on the vcds
