What Are Normal Fuel Trims for S6?

A6 All/ S6 All
#1

Just as the title states, what are the fuel trims supposed to be? I have searched the forum and the web but cannot find a good answer. Supposedly, most cars have a tolerance of +/-10 before setting a code. Anyone know what the range is for the 5.2L V10 S6?

I have another thread where I talked about my issues of trying to chase down a vacuum leak.

I think I may have my problem fixed but to know for sure, I need to know what normal fuel trims are supposed to be.

Also, is it normal on cold start up for the Short Term Fuel Trims to run +20 and the settle down once the cats are warmed up? Is this the Air Injection doing this to warm up the cats?

#2

25% will max out the trim and trip a fault.

yes to SAI adding air to the exhaust and it goes rich to compensate. Well, mainly goes rich to light off the cats and warm the engine up asap.

+/- 3% on average is normal on long trim after some cruising, will fluctuate up to around 5% or so if you have a lot of pedal modulation.

if you have a vac leak or injector sticking open STFT will peak 25% then the long terms will peak to 25% and will have MIL on

#3

My vacuum leak must have been just enough to set the P1081 and P1085 codes but not so bad as to cause super high positive trims. I think Audi must have a bit tighter tolerance for the LTFT’s than the common +/- 10%.

My idle LTFT’s were around +5% on all banks and I was setting codes off after about 25 miles of driving.

After removing the intake spacers, my idle LTFT’s are 0.8, 0.7, 1.6, and 1.8. STFT’s are also not swinging near as wildly as well. I can’t confirm my problem is fixed but fuel trims immediately started looking better.

I am in the process of changing out my valve cover gaskets as they were leaking oil into my spark plug holes. I am sure they contribute a little bit of a vacuum leak.

#4

lean codes+ intake spacers…did you remove the motor lift brackets? they will prevent the IM from touching down properly…

#5

Yup, I removed the rear two and the two in the front and the small bracket that held the vacuum hose.

It wasn’t until I removed the spacers that the lean codes have not come back. I won’t say for sure yet that this was the problem as I am still monitoring. But I eliminated every other possibility.

#6

What measuring blocks do you use for fuel trims?

I just tried 032 and 033 per the VCDS YouTube video, and it didn’t look right.

Thanks.

–Alex

#7

Remember there are two ECU’s and I think you need to pull trims from each ecu as each ecu represents one side of the motor.

Post a pic of what you see in those blocks. I remember them being 032 and 034 on the older ECU. The values shouldn’t move around a lot. They are averages. So you wouldn’t log them you would just capture the data from them.

#8

Since there are two ECU’s (Master and Slave), there are a total of 4 LTFT’s and 4 STFT’s. I used the VCDS module of Engine Other and then data block 032 for the Long Term FT’s and 033 for the Short Term FT’s (if I am remembering this correctly).

#9

http://audirevolution.net/addons/albums/images/990904462.png

http://audirevolution.net/addons/albums/images/158023355.png

Those are what I’m seeing. Based on the videos I’ve seen, I was expecting more labeling if these are the fuel trims. Group 033 Lambdas are cycling as expected. I can’t imagine any fuel trims reading zeros. Hence my confusion.

Thanks.

–Alex

#10

http://audirevolution.net/addons/albums/images/990904462.png

http://audirevolution.net/addons/albums/images/158023355.png

These don’t look bad. But these look like they are from a quick start and not a longer driver. They tend to reset themselves. You would have to take a short drive and then capture the data.

#11

Ah, yes, it was from a quick startup to grab readings. I had assumed that long term trims were stored through restarts.

So based on my readings, 032 A and C are long term trims and B and D are short term, correct?

–Alex

#12

Group 32 are the Long Term FT’s. The 1st and 3rd numbers are the idle LTFT’s. 2nd and 4th numbers are part throttle LTFT’s. Engine I is bank 1 and 2 (I think). Engine II is for banks 3 and 4.

Group 33 are the Short Term FT’s. The 1st and 3rd numbers are the actual trims and the 2nd and 4th numbers are the O2 sensor voltages.

#13

Sorry Alex I though I responded to this. Its best to capture them after a short drive after the car has gone through its warm up phase. Also keep in mind as posted just above.

You have two banks of the motor but 4 02 banks. So you need to look at all 4 searching into both ECU 1 and 2.