Theoloop

Hello everyone.
My car is running a little choppy at idle, no cel lights, vcds registers 1-3 misifires at idle but that doesn't happen very often.
Went through all of vcds and everything seems to be within spec, iat,maf,lambda, timing.

The only red flag that popped up is that the bank 1 sensor 1 o2 reads at 1.45 volts and fluctuates between that and 1.55.
Rear 02 reads .27V steady.

does the front o2 seem bad even though i do not have a cel?

markcm

I have the same question so rather than start another thread, I'll bump this one. From what I understand, the upstream O2 sensor should oscillate between about .1-1v volts when warm and idling. Mine is not oscillating much and fairly static around 1.5v when at idle. Is there something unique about these sensors (2010 2.0tfsi) or is this sensor bad? I have a P0420 code and my LTFT changes rapidly (I am used to older B7 where LTFT would only adapt every 15 minutes or so, mine is constantly moving and averages around +7 but moves between about +2 and +14.

audichobo

@markcm Did you ever find out what the issue was? or is it normal to have 1.5v reading?

SMac770

Engine questions without specific identification of the involved engine, by using the three or four letter engine code, are not particularly useful. The OP, if the question is about an '06 A3, is likely about an EA113 engine with LSU 4.2 sensor. The next post is about an EA888 engine, with LSU 4.9 sensor. In either case, the voltage is not the measurement value. The current flow is. The ECM simply advertises a voltage value as a pseudo value for those still using archaic methods. You need to monitor the lambda value rather than the voltage, at least on the front lambda sensor. The back jump sensor is still an old style voltage value, iirc.

audichobo

Thanks for kind reply @SMac770
I have 2011 Audi A4 2.0tfsi. I searched for o2 sensor readings and found that they should fall within a range of 0.1 to 1.0 volts. However, my readings are showing 1.45 to 1.55 volts, so I asked about the voltage, but I guess I should've been looking at the lambda value huh? my ECU is a UDS protocol so I am not able to use the measuring block option. do you know if there is a way to measure the lambda value for UDS protocol? also what should the lambda value should be?

audichobo

Just measured lambda value at idle and it was around 1.0. I guess this is normal at idle to run lean. But does this mean my fuel/air ratio is good or should I monitor lambda to max rpm?

SMac770

So you'd have a CAEB engine like mine. Again, ignore voltage for the lambda sensor (the pre-cat O2). It's about the lambda value, not any voltage value. And lambda 1.0 is stoichiometric, not rich or lean. The actual A/F for lambda 1.0 varies with the fuel mix. E85 for example is a different A/F than E10 gasoline for stoichiometric combustion.

https://www.audizine.com/forum/showt...1#post14754997

What's your purpose, what's your question, in asking all this? And if you're logging lambda or any of these values, you need to do Group UDS if VCDS. Otherwise, it only samples one parameter per interval, and it can take over a second for it to get consecutive samples of a particular parameter. Which is generally useless for cyclic patterns like these.

audichobo

@smac770

I don't have any error codes but my fuel consumption isn't very good and I see misfires on all my cylinders. maybe 5-10 misfires every 500km. Just starting to check some sensors and learn these things. Might attempt to replace cheap items first such as MAP sensor and spark plugs etc..

SMac770

I'd suspect injectors, but spark plugs is a good start. You don't have a MAP sensor on an CAEB. If you mean MAF, what are you seeing for g/s at idle and at WOT? Should be 2-5 g/s at idle, peaking around 160 g/s during WOT. What is your long term mix fuel trim?

audichobo

@smac770
I don't have the fuel trim values, how can I measure this? Also I tried to measure MAF reading but wasn't able to find the option in VCDS since I can't use measuring blocks.
As for MAP sensor, I will have to check my car later but I saw a video of a guy replacing this : 038906051E.

For injectors, I might try to use fuel cleaner, have you tried this? kind of skeptical about seafoam as my car is 2011 and they say if it's old seafoam can make things worse..