Still Battling EVAP Issue

[christianb5s4]

Quick update. When I checked if there were any pending codes last week, the P0456 code had re-appeared (although only in pending, not a stored code). However when I checked it today out of curiosity, there were zero pending or stored codes. That means it went away on its own which it's never done before. I'm keeping my fingers crossed on this and will report back after more miles.

[christianb5s4]

To provide a long term update, the car has had zero codes and the EVAP issue appears to finally be resolved. The fix was properly re-sealing the VVT covers which were done very poorly (and using incorrect sealant) by the dealer I bought it from. I'm sure other parts I replaced helped but this was the real fix.

After several hundred warm up cycles, varied driving conditions, etc, no code and seems to be truly resolved.

[christianb5s4]

Welp, the code is back. Now it's P0456 EVAP leak: small leak. Now it comes back as soon as I clear it.

This feels like something electrical i.e. a solenoid that has failed because it was sudden and immediate code. Does anyone know what solenoids are related to the EVAP system? The car already has a new 'N80' solenoid but I believe there are several other solenoids that are in the engine bay related to the EVAP system.

[4.2 prototype]

VVT leaking again?

[christianb5s4]

Nope, definitely not. The code is no longer there and cleared itself. It was odd this time because the code wouldn't clear with VCDS or a generic OBD2 reader, but now is no longer there and fixed itself.

At this point who knows but it seems electrical to mee. Like a solenoid somewhere buried in the EVAP system that is failing or occasionally getting stuck (car already has a new 'N80' purge valve). Almost everything EVAP related is brand new and OEM.

[4.2 prototype]

Delete/code it all out like the B5's amirightttt

[christianb5s4]

Ha, I wish! B5 life is so easy because you can code out EGTs, EVAP, rear o2s, etc.

[4.2 prototype]

Lol yea my RS6 has nothing in the engine bay ha.

[valet]

Had a similar issue with a 180 hp tt I once had. Couldn't for the life of me figure out where the damn problem was. Finally got fed up and spliced in a check valve inline after the detection pump and the problem went away. Turns out the detection pump was being a lil bitch. Smoke test and vcds didn't tell me that though.

[christianb5s4]

Had a similar issue with a 180 hp tt I once had. Couldn't for the life of me figure out where the damn problem was. Finally got fed up and spliced in a check valve inline after the detection pump and the problem went away. Turns out the detection pump was being a lil bitch. Smoke test and vcds didn't tell me that though.

I replaced almost everything EVAP related, including the leak detection pump. So I doubt that's the problem unfortunately. Nothing to do right now since the fault went away so I guess we will see if it comes back at some point.

[KaMiKaZi_t0M]

Thankfully I can say this has been finally solved. I had the high pressure fuel pump replaced as there was some evidence it was leaking oil slightly and leaking internally. At the same time, all EVAP lines were double checked and verified there's not a single leak. So we went back to the basics, checking out stock Audi photos of the C6 3.0T engine bay and discovered the cause.

The EVAP line that should connect to the purge valve was connected to the intake and the PCV line that should connect to the intake was connected to the purge valve. Doh. Whoever worked on the car prior to my ownership put them on the wrong way around. No codes at all, car runs and starts smoother, power is more linear, gas mileage is up and I filled the tank and had no issues starting after fill-up.

I just want to thank you for posting this and saving my sanity. I work at an european independent shop and we've been battling this code for years, customer has just dealt with it until it was emissions time. We've had the intake / supercharger off multiple times and each tech put the hoses back the way they saw them (which was backwards just like yours).
I owe you a beer man, and this just shows how important it is to document what you do and keep good notes. By you taking the time to post this you saved me.
I miss my B5 S4 everyday

[christianb5s4]

Glad that helped! I only figured that issue out after digging for some stock photos of a bone stock C6 A6 3.0T engine bay, and discovered that. The EVAP small leak code still comes back for me every few months then vanishes for a long period of time. I've given up.

[Rodizzle]

however for the first time since I bought it it actually stayed running instead of starting then stalling then having to restart it again.

Bring back from the dead , Christian did u ever solve your P0456 code ? For the last couple of weeks Iv occasionally had trouble with starting the car . Like you said it takes longer then usual and once in a while it stalls then I have to restart it . I haven’t paid attention if it’s only when the tank is full of fuel . Regardless it’s annoying , I first thought it was my lpfp or even injectors but after logging the car , everything was normal nor feels any less different .
Not until yesterday that I got a p0456 and today again , this is what got me searching and came up on your thread . Everything makes sense now , I’m guessing the p0456 is related to me longer starts .
It’s annoying that’s all lol .

-Ro

[SinCio]

Too soon to tell on the oil consumption, granted I didn't measure consumption before it was replaced so I can't tell you what change it made. After a bit more time I'll let you know if I have an issue or not!

I replaced the EVAP valve with a brand new OE part from the deal which is this one as well as the breather hose that connects to that valve which has an integrated check valve:




However the reason I believe it's either the leak detection pump and/or the charcoal canister is because the system on block 070 passes the test when the tank is 1/2-full but the codes come back as the tank gets lower, the hard start after filling up as well as smelling fuel vapors while pumping the gas also remained. However I do not have issues with the pump stopping and fills normally.

Do you have a part number for this? I'm starting the battle against a P0455 myself.

[jerome_c7]

Hi Christian, first time ever posting on a forum, never took time to create ean account. Wanted to say you a big thank you! Ive switched my hoses too ! I tought it was my purge valve too, engine stalled everytime after i refuel. Thanks again for your post/update :)

[sdhildebrand]

Thank you so much for actually posting the solution! I had this exact same issue after replacing the Pcv. My mechanic (me) also crossed these two hoses. Such an easy fix after reading your post.

[andrewrico]

Thank you so much for actually posting the solution! I had this exact same issue after replacing the Pcv. My mechanic (me) also crossed these two hoses. Such an easy fix after reading your post.

Hey mate do you have a picture of the hoses that were crossed having some trouble too.


Sent from my iPhone using Audizine Forum