lean condition worse under load?

B6/7 S4/RS4
#21

well I pulled apart that hose and took out the thing inside, turns out it’s just a vacuum cap. Definitely not supposed to be there, lol. I think I’m the 6th owner of this car, who knows who put that there or how long it’s been there but now the IM flap is working for the first time since I’ve owned the car.

I was pulling off the rear bumper so I had access to the little vacuum chamber thing in the back left fender, and this is what I saw:
http://audirevolution.net/addons/albums/images/903577051.jpg

I believe that solenoid controls the muffler flaps? Is it supposed to have that open nipple on one side?

#22

also, I tried testing the rear muffler flaps with vagcom by running the car for a minute to generate a vacuum, then going to output tests and activating the rear muffler flap solenoid. When I do that, I can hear at least one of the flaps moving because they squeek when they do, but it/they only move a few times before they run out of vacuum and stop. is this normal? I know they only have the limited amount of vacuum stored in that reservoir after the car is off, but I’m not sure if it should last longer than that. I can’t tell if they’re both moving or not because it doesn’t even last long enough for me to click the activate button and then get back there and watch them move.

#23

actually forget about those last two posts, sorry, I did some searching and found the answers for myself.

Something else I hadn’t thought of until now, is that there’s a good chance this exhaust leak has nothing to do with me messing up the reinstall of the exhaust and instead was caused by my car being rear-ended a few weeks back. It seemed minor with very little damage but who knows. I was already trying to figure out a lean issue before that happened so I’ve just been assuming that my lean issues were related to the work I did, but the vac leak could’ve been the only issue I had before and then maybe the accident caused the exhaust pipes/manifolds to crack

Last night I started dripping coolant and when I woke up the res was empty, the issues just keep piling up. fun fun

#24

well I just made a smoke tester out of a cigar, a plastic bottle the right size to be shoved into the exhaust pipe, some hose, and my air compressor. The exhaust was cold and I didn’t use much pressure but I wasn’t able to find any obvious leaks (only 1 side was really tested well, the other side didn’t get much smoke before I ran out of cigar and melted the bottle but my lean issue must not be exhaust leaks if at least 1 side is fine, since both banks are lean). Next I’ll smoke test the intake and vacuum lines, maybe there’s still another leak there that I haven’t found

are the front and rear O2 sensors the same? if I don’t find any more vacuum leaks then maybe I will try and swap the O2’s front to rear. Another thought is the copper anti-seize on them, I tried to be careful because it says it can foul them out if it gets onto the sensor part but maybe that’s what happened. I have piggie pipes and spacers on the rear O2’s btw (so far the spacers have been working for me too, no codes for cat efficiency), don’t think that matter but just fyi.

#25

still working on this, haven’t smoke tested the intake yet but I thought I’d show you the knocking sound I was talking about. (This is actually more concerning to me than anything else but I was focusing more on fixing the lean issue first in case that’s what’s causing this issue). So here are a couple videos… really hoping this is something like an ignition knock that wouldn’t be too hard to fix, as opposed to a bad bearing or something like that

https://youtu.be/L4H9Y1QcCyI
https://youtu.be/nfj97MVdurA

#26

ok lots to cover so Ill see if I can get to it all.

The front and rear 02s are very very different so they cant be swapped. They need to be in there place.

As for the muffler flaps you are only going to get 2 maybe 3 flap changes on the stored up vac resivware vac.

Usually smoke testing the exhaust is hard because there are going to be valves open on the exhaust side of the heads and it will take a ton of smoke to build up pressure to leak out. Also some exhaust systems will expand when warm thus causing even more issues and making it even harder. One good way is to look under the car for carbon build up leaking out at the connection points

#27

thanks again for all your help.

I don’t think there were any valves open when I smoked the exhaust, at least not on bank 1 which is the side that got a lot of smoke. I could tell it built up some pressure because there was a little bit of smoke escaping out the back where the plastic bottle didn’t perfectly seal to the pipe, but it was shooting out like it was under pressure (I also used duct tape to help seal it up but the smoke pushed through and created some small leaks in the taped area). I set the regulator on my air compressor almost as low as it would go and still blow out air, it was somewhere below the 10 psi mark. I wonder if I could have a leak that would take more pressure than that to show up? is there a lot of pressure in the manifold/pipes while the car is running?

The main reason I thought there was an exhaust leak was because of a noise I hear while it’s cruising, but now it’s looking like that noise is from something else. What do you think about the way it sounds at idle?

#28

Usually as a rule of thumb there wont be a side where all the exahust and intake valves are open or closed. At the motor always has at least two cylinders that are on compression and two that are just after or in exhaust. since its a V there should always be one if not more that are going to be open. Still at some point the cylinder will fill and then back pressure will happen so if you got enough pressure it should have been fine.

Are there any different codes that the ECU has

Its hard to make out the faint low tone on idle. It definitly sounds like something is out of the norm its just hard to make out the faint low tone.

#29

right my bad I wasn’t thinking, of course there were some exhaust valves open. I just meant it didn’t have any problem building up pressure. for some reason when I read your comment about open exhaust valves effecting the test, I read “open exhaust valves” and thought “open exhaust and intake valves at the same time.” I’ve heard that can be an issue if a cylinder is at tdc right between an exhaust stroke and an intake stroke, depending on the engine/cams.

the only other code I’m getting right now is for a radiator fan being jammed/restricted, which is odd since I can reach a screwdriver into the one that doesn’t come on and turn it and it doesn’t feel jammed at all, but I’ll worry about that after I figure out the engine problem

#30

The rad jammed code can mean you have a dead fan. The fan itself isnt turning on or never gets up to speed. That is something to look into. Depending on where you live it might not be an issue for the next few months given the cooler weather coming in

#31

I noticed that there was a small oil leak coming from the passenger side cam sensor (the ONLY oil leak remaining after everything I did while the motor was out), and it must have been leaking some vacuum through the pcv system as well because the fuel trims got a little better after I replaced that O-ring. That definitely wasn’t the main issue, the long term partial trims are still at 14.8 & 15.6, but it helped a little.

I tested the IM for a vacuum leak by sealing up the throttle body and then blowing air into the IM through a vacuum hose and then plugging it shut - none of the pressure leaked out until I unplugged the hose so there must not be a vacuum leak at the manifold. I did a separate test for the line that runs from the charcoal canister to the n80 valve and it was fine, and I also separately tested the line that supplies vacuum to the rear mufflers and nothing leaks there, either. There are only other possible vacuum leak might be the line goes into the other vacuum canister under the front left wheel housing liner and then from there to the leak detection pump. If I disconnect that line from the front of the manifold and try to blow through it I can’t, but I’m not sure if there’s another check valve hidden behind the wheel housing liner. If there is a check valve then I still could have a leak on the other side of the valve, but if not then that line is fine. Do you know off hand if there is a check valve hidden behind the front left fender where the vac canister is?

I tried using a stethoscope to find the knocking sound and I’m still unsure but I think it might be coming from the serpentine belt. It’s either coming from there or from somewhere under the bank 1 valve cover so I sure hope it’s just the belt! The sound is a lot more obvious in person than it is in the recordings, I guess my phone’s mic isn’t picking it up very well, so that sucks. When I had the belt off I noticed a couple really small chunks missing out of it but it wasn’t in bad enough shape to need replacing, maybe it has more chunks missing now and that’s what’s making the noise. When I have time I’ll put it back in service position so I can run it without the belt and see if the noise goes away

#32

I forgot to mention, I also ruled out a leaking brake booster (I already knew the line was fine but I read they can leak internally) by temporarily disconnecting the vacuum line going to it and capping it off, and that made no difference in fuel trims. And I followed the ELSA procedure for testing the combi valves by trying to blow through the SAI pump’s intake while the valves were closed, and I couldn’t blow any air through so that means they’re not stuck open. My serpentine belt has 34k miles on it btw.

#33

Well first thoughts sound like you have covered most of the bases.

next it sounds like you might want to shift the injectors from one side to the other to see if the lean code follows

#34

oh TY that’s a great idea! Why didn’t I think of that, lol. I just swapped them to the opposite sides. I was getting the code on both sides but one bank was a little worse than the other so I’ll be able to tell if it switches sides. About to go for a drive and see if it re-adjusts

btw I did a compression test recently, not as part of the troubleshooting for this issue but just because it’s something I’ve been wanting to do for a while. I put the results in the compression test thread.

#35

Thats not bad compression results. I just saw that. Let us know if the lean issue followed the injectors or if its still on one side. Do you still have your cats in

#36

I have the main cats but not the precats. I drove for several thousand miles without any codes after gutting the precats so I don’t think it’s related, although I still think there might be an exhaust leak.

Here’s what it looked like before swapping injectors:

https://drive.google.com/file/d/0B6GNncUmcvCzNkJueFdmdkcxTHM/view?usp=sharing

it was consistently showing a few points higher on bank 2 before the swap, now after swapping it still varies some but it’s always a couple points higher on bank 1. So I think the injectors are contributing but I doubt they’re the main cause of the issue. I don’t see how both sides would randomly get so clogged up they cause a 15% increase in fuel trims after running fine for a long time. I always use quality gas, 91 from either shell or chevron which is the highest octane available here.

p.s. I’m about to post another thread for a different issue I have with the knock sensors. I haven’t mentioned them in this thread because I’m sure an issue with them wouldn’t affect fuel trims at all, would it?

#37

I wasn’t sure if that image link would work, forgot I still can’t edit my posts. I just started using google drive and I’m not sure how to embed an image from there. let’s try this…

http://audirevolution.net/addons/albums/images/603682119.jpg

#38

and just to be clear that’s before swapping. after swapping it’s varying between 15-17 on bank 1 and bank 2 is always a point or two lower than bank 1