11ish mpg ?

[Trile]

Ok so, I already said I ordered 2 new front o2s... and didn't expect them to come any time soon, with all the holidays etc.

So today I swaped the rears in the front and vice versa, went for a short drive, got home, cleared one code (for o2 sensor ofcourse) and logged it in idle, all warmed up.





I took the first photo when there were no misfires. bad example.
The first 3 cylinders had no misfires for the entire time I logged (3 or 4 minutes).
cylinders 4,5 and 6 had an occasional missfire or two, and at one point cyl 4 had 2 misfires, cyl 5 had 4 and cyl 6 had 3 (example) . So just that bank. Is that something to be worried about?

Also logged the mixture adaptation channel as advised (thanks @ThirdStrike) and as you can see it shows 1.1% in the first box and 0 in the second. From what I read on the rosstech site, the second box showed zero probably because I just cleared the codes.
What does your car show when you log this channel (first 2 boxes) ?

and as luck would have it... 10 minutes ago the mailman arrived with a package. The new sensors. LOL. So I just wasted time and money swapping the rears (had a shop do it, I don't have the tools nor the time right now).
And now I have to do it tommorow, again :) This time with the new sensors.

Thoughts and comments more then welcome :)

[julex]

Don't feel bad. I can get anywhere from 11 to 19 mpg on the same exact route depending how I drive the car on a given day, that's on allroad though (much heavier and different gear ratios but the same engine):

To go 19mpg I never go with RPMs over 2k. I never accelerate faster than what I could do on my bicycle. When I approach part of road where I need to slow down, I use engine to slow dow., I am bascially hypermiling. Somewhere over 2.25 or 2.5k the MPG plummets down for some strange reason.

When not caring about mpg I just gun it. Stage 3 going full boost takes enormous amounts of fuel.

[Trile]

I understand what you're saying... but It's not like I bought the car expecting great mileage.
It's been getting progressively worse in the last few months.
And I regularly fill up half a tank and drive like you explained in the 2nd part - like a bicycle. Never over 2200 rpm. Never boosting.
I just want to get the same (or similar) mpg like the other s4 owners hear are getting.
I'm just stage 2 and I should NOT need half a tank to do 65 miles.

[julex]

stage should not matter if you're never boosting unless you have some really large injector that might have issues atomizing fuel which would lower your engine efficiency (1000CC and larger). WIthout boosting, stock, stage 1 and stage 3 should always get the same mpg if driven the same way.

Sounds like new O2s should improve your situation. They sometimes take a dump without causing any CELs.

[Trile]

can anyone let me know if the logs look OK ?
do i have to manualy inspect the fuel rail and injectors if the log shows the mixture is OK ?

[wannabeS4]

Did you ever solve your issue? Im currently getting about 15mpg mixed with no boost and cels. Would like some help?

[zrider91r]

Im curious as well, I am also getting intermittent O2 sensor CEL, but i cleared it a couple hundred miles ago and it hasnt come back on yet.
I dont know what the policy here is for posting links to other vendors(so I'm not going to post it), but there is a place here in the states that sells almost everything pretty cheap.

[ride1157]

I have no codes at all car is healthy (checked with vag com)... I avg 14-15mpg most of the time and 17 driving highway and city mix, actually to put it better i barley get 210-230 miles to a tank. I'm almost stumped as well but i think maybe my pre cats are plugged or something. ( i got a code for rear o2 before i tuned the car, then i got it tuned and chopped main cats off) This helped a little but still bad. Since my avant is a tip doing the downpipes (piggies) is a lot harder than my 6speed. My six speed gets 23mpg (no cats custom exhaust) combined same driving habits...

[wannabeS4]

Im curious as well, I am also getting intermittent O2 sensor CEL, but i cleared it a couple hundred miles ago and it hasnt come back on yet.
I dont know what the policy here is for posting links to other vendors(so I'm not going to post it), but there is a place here in the states that sells almost everything pretty cheap.

Post the link or pm it to me if you want.

[BerlinCity]

I just changed my precat o2 sensors 3 hours ago. I was throwing a code that stated something like inefficient warm up. I am also getting terrible gas mileage and I'm only stage 1+. I don't have a vag com yet so I will have to go to advanced auto parts to get the codes cleared. I will try to let you know if my fuel mileage improves. Wish me luck.

The labor really wasn't that bad. Took me about 2 - 3 hours. I used the below DIY and definely recommend the o2 sensor tool.
http://forums.audiworld.com/showthread.php?t=2775139

Fuel filter DIY below as well. Was going to do that tomorrow because it is easy, but I would really like to know how much of a difference the new o2s will make.
http://www.audizine.com/forum/showth...he-Fuel-Filter

I really hope it's these primary o2s and not my cats. If it is my cats, will I have to purchase entire new downpipes or can the cat be replace separately? Thank you for any answers on this.

Trile - good luck!

[Trile]

swapped the front o2s with the rears - it did help the mileage.
but now i also get a code for the front o2s. intermittent.
I am waiting to install my catless downpipes and then Ill install the new front o2s.

Can a fuel filter get clogged in 5 months if I regularly drive with the fuel light ON ?
Also, is cleaning injectors worth it ? I can get them cleaned for quite cheap. Maybe that can also help.

[BerlinCity]

I just wanted to give some feedback about my recent oxygen sensor change. My gas mileage has definitely improved. I believe by at least 4 mpgs. Unfortunately one error code came back after about 50 miles. Erased the code, hoping it wouldnt come back, but it did after about 180 miles driving down the thruway.

Code: P0421 warm up catalyst efficiency bank 1 below threshold
Before the o2 sensor change I had it on both banks. I have no idea why this code came back. Could it be that my cat is dying/dead?

Any help would be appreciated.

Thanks

[s4cappa]

maf sensors can make the car have bad mileage and not throw a code

[BerlinCity]

Should you upgrade to a better maf sensor even when you don't have upgraded turbos and which one would you recommend? Also, is therE a way o test the maf sensor? I've cleaned mine before but don't know if it's bad.

Thanks

[s4cappa]

no you shouldn't upgrade to a bigger maf if your not stg 3. you will get fuel trim codes. I just changed it out with another s4 i have to check it but i guess you could find a friend who would swap out for a day just so you can check it out.