This started happening only after i had rear O2’s replaced a few weeks ago. Thats when this flip flop from too rich to too lean on both banks started happening.
This started happening only after i had rear O2’s replaced a few weeks ago. Thats when this flip flop from too rich to too lean on both banks started happening.
And I totally agree, it doesnt make sense at all. Thats part of why this is so frustrating. Tired of chasing my tail disgnosing stuff that really should not even be an issue. None of it makes sense.
Is it at all possible my front 02’s are swapped? Minded, this crazy LTFT swing was not present until recently.
I am guessing there has to be something wrong with how the 02 sensors were connected at firewall.
Another odd thing is the p/n on the rear O2 sensors removed from car is
078 906 265. This seems to coencide with upstream or front O2 sensors. Something is seriously goofy here.
Need to clarify. Both banks, front 02 reading rich. Then both banks, rear 02 reading lean. Didnt think I was supposed to get cat efficiency codes with tune?
Went through process of verifying sensors are all in correct locations both at harness and corresponding exhaust stream. They are. Through on a brand new maf to see if g/s are inline with old maf readings as my old maf was reading over 9 g/s at idle on cold start which seemed a little ambitious. The new maf is not reading much different.
I am at a loss here. I guess I can try replacing front o2’s but I am not confident this will resolve anything as the have less than 15k miles and my vagcom states they are “ok” after cycling through readiness and test output. This is really annoying and frustrating.
What did jhm say?
Wanted to chase down easy mistakes before bothering them. Reached out to CV to ask about simple things to verify first and check off.
Man this sucks, I feel your pain. It’s been one thing after another since you supercharged it, reminds me of my car. Hopefully you track it down soon. Glad they’re still talking to you at least, they completely ignore my emails now. CV is the greatest guy ever and I consider him to be one of my best friends. He’s also the best JHM employee there is and he doesn’t even work for them.
Hmmm, that’s disappointing to hear. And ya it has been one thing after another. Car has never been 100% since getting it back. I do hold out hope it will be at some point, but that faith only goes so far I guess.
Are you still getting mixed rich and lean codes…
Yes. To be clear, rich front codes both banks followed by lean rear codes both banks. In pairs. Flipflop after about a week of in town driving (few miles) and clearing codes.
Nothing has changed aside from verifying that the sensors are connected in correct orientation at the harness and exhaust stream.
Nothing 3 days after receiving email with codes I had been and am currently getting.
Emails just sit there. Get someone on the blower. Or show up.
I think that he lives a little far away to just show up. That would be like a two to three day trip to actually have time to get stuff done.
Happy, let me read through this and see what helpful things that I can suggest.
Always helpful…and appreciated. I am thinking vac leak, exhaust leak, fuel delivery, tune. In that order. Will be going over everything (again) to try and get this sorted once and for all (at least longer than a couple weeks). First thing I am doing is going through every vac line, clamp, exhaust fitting, O2 sensor thread, etc to be sure everything is fastened and attached correctly. Will be replacing fuel filter, checking my fuel pump, then on to fpr and injectors.
I do wonder if the tune is just unable to perform and adapt at this elevation. Would not be the first instance of an issue that a piece of hardware was blamed as culprit (maf sensor) and unnecessarily replaced (did not resolve issue) to find out a tune revision did the trick.
Seems weird to me that I never had a front O2 rich code for both banks, replaced rear O2’s (response too slow and no activity) then bam, front O2 rich codes not a couple weeks later, followed by post cat sensor too lean codes after clearing. Thing is my vagcom runs through readiness and tests and all sensors/system say “ok”. Which tells me they are ok and operating correctly, and doing their job.
Another concern or thought I have is if this is realated to the allroads fuel delivery/return system that Jason was mentioning was one of the differences between it and the S4?
Actually, Jake is really good about hitting me back. My guess is they are just as puzzled as I am frustrated. Believe me, I have thought about putting it on a trailer more than once to have it sorted out since bringing it home.
Ok, I had to go a bunch of pages back to the point that you got the car back from JHM with the 0A3 transmission (page 11) because a few things bothered me after reading this.
The current problem that you are having is the long term fuel trim too rich and too lean codes right? Please confirm that.
This is what I noticed after reading today/tonight:
- You had MAF implausible signal codes so you replaced the MAF and redid the wiring.
1a. By the way it is probably not related but I compared your highest MAF reading of 244 g/s to my 329 g/s and that seems really low but the ECUs could read differently so that would be something to ask JHM about at a later date. It took going through 70 pages of Photobucket pictures on my account to find that old log. - The readiness codes showing ok is not relevant to the fuel trim codes. I am a little more informed about how that system is set up and I am pretty sure that they would not appreciate me giving that information out so please just trust me there.
- If you were getting no activity and slow response codes for the rear oxygen sensors and after you replaced the sensors those codes did not come back then the rear oxygen sensors were probably bad and needed to be replaced.
- I don’t think that the rear oxygen sensors are causing the fuel trim codes at all and it is something else bothering the ECU. These V8s use six wire wideband front oxygen sensors from the factory and with the stock ECU programming the ECU goes off those front oxygen sensor readings for all fuel trim corrections. The rear four wire oxygen sensors are only responsible for monitoring the catalytic converters with the stock ECU programming. There isn’t any good reason that I can think of to change that portion of the software with aftermarket tuning because the four wire rear oxygen sensors can only read rich or lean as the six wire front wideband oxygen sensors can tell the ECU how rich or lean the mixture is.
- One of the reasons that I had to go so far back in this thread is to check what exhaust system that you have. I saw that you said that you have the 2.5 inch FI catless downpipes and the MagnaFlow 2.5 inch catback. It looks like the Magnaflow catback exhaust necks down to stock in the middle to bolt onto a stock car so do your catless downpipes neck down or did the neck down portion of the catback get cut off and 2.5 inch flared extensions get welded on to accommodate the down pipes? The reason that I ask is because the downpipe connections at the exhaust manifolds can be tricky to get right even with stock downpipes and the stock catback because the downpipes have to be angled to connect to the catback. A botched connection of the downpipes at the exhaust manifold can cause both rich and lean fuel trim codes.
- The fuel system is different on the Allroad V8 in some ways than the B6/7 S4. The first thing that is instantly noticeable is that the Allroad uses a return fuel system with the fuel pressure regulator at the end of the fuel rail as the fuel pressure regulator is built into the fuel filter on the B6/7 S4s and thus they use a returnless fuel system from the fuel rail. The fuel pressure regulator on the Allroad does have a vacuum reference so that can be affected by manifold pressure changes from vacuum to boost but I am pretty sure that the ECU tune would take that into account.
Final thoughts:
I would double check the downpipe connections at the exhaust manifold to make sure that they are fully on correctly with all six 13 mm nuts tight. Especially with the rich codes coming in after replacing the rear oxygen sensors because something could have been shaken a little loose. After that I would check the vacuum line from the fuel pressure regulator to the intake manifold to make sure that vacuum line isn’t damaged. If both of those are good then I would replace the fuel pressure regulator because it is cheap at $32 for the Bosch unit from ECStuning. Those three things are cheap and fairly easy to check if you can DIY. Good luck!
https://www.ecstuning.com/b-bosch-parts/fuel-pressure-regulator/078133534c~bos/
Hell of a response Jimmy! Lucky to have a member like you on the forum to give some really actionable advise here!
I try I try.
Thank you for such a robust and detailed response. To confirm, I am getting front O2 too rich codes on both banks, followed by rear too lean codes on both banks after clearing codes. Then back to front too rich.
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Yes I was getting MAF implausible signals. Wiring was checked and tidied up and a new maf and original maf were both still kicking out same implausible codes. A revised tune was provided, loaded and cleared up the issue. Explained to me that everything was opened up to help match the blowers efficiency and more specifically, decel off throttle sensitivity.
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Fair enough
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Agreed. The rears needed replaced. B2S2 was throwing slow response/no activity. Both rears replaced with oem units.
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Front sensors too rich codes, rear sensors too lean codes. Always in pairs for both banks and alternating front followed by rear.
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It is a FI 2.5" catless dp mated to a MF 2.5" modified to be 2.5" through. Very interested in this as I had concerns from day one about my exhaust sounding “tappy”. Was assured that it was just how my exhaust sounded. When the car was in shop and up on lift for something else (possibly rear sway bar issues or ac issues, forget now) I asked him to inspect the exhaust setup for any noticable leaks/issues. Sure enough, every one of the 6 dp to manifold nuts were no less than a full turn loose. Shop tightened them down. Guess we need to investigate this some more to be sure nothing else is going on or if they backed off again?
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Thanks for confirming. And I would think if anything in tune needed to be accounted for relating to this would be. Certainly given them pointing it out from day one drop off.
Thank you Jimmy. I will and can double check everything pointed out. I hope it is as simple as those 6 nuts backing off some again. What makes me believe it wont be this easy is I was not getting too rich codes when they clearly were loose months ago? But, will still verify. Also see about replacing fpr.
Thanks again for the insight and help. About the maf max g/s, isnt a general assessment for maf readings 80% of rated engine hp? If so, that 244 would be fairly spot on with the allroads 300 hp rating. Maybe thats wrong? Thanks again man.
Will get through this with everyones help, just a bit frustrated and surprised with so many nagging issues and mistakes.
New fpr and fuel filter ordered. Cheap maint items and easy enough to replace.
Jimmy is the man.
a few things to back up all of that. keep in mind your MAF reading is going to be much lower due to your elevation. So that isnt a big deal but the exhaust system is something you should really check out.
Here for me is a big red flag. After you changed hardware you started getting new codes. New codes after hardware changes or car work usually point to something that popped up after the change.
There is a good chance that you might have created an issue in changing the sensors. lots of stuff gets disturbed when you change sensors.
After you go and make the changes on the fuel pressure and on the fuel filter. Try clearing the codes and then unplug the rear 02s. From there see if you end up getting rich codes still. Unplugging the rear sensors and checking to see if things change in the codes will help continue to give you more information.
At one point the car ran fine without rich codes correct.
Thanks Justin. It was not getting rich codes at one time. Only after replacing rear O2’s a few weeks ago. I thought finally, all my sensors are new and fresh, car should provide me hassle free fun. Nope >:( The car has not ran code/dtc/mil/limp free for more than a couple weeks since driving it home whether it be the ac, maf, the rear O2 codes to the current front rich/rear lean codes. I appreciate your help and response. Will be sure to go over everything and report back.