EVAP Witch Hunt!!!!!!!!!!!!!!???

[Mosquito]

unplug your evap sensor. youll get a cel but it will stop misfiring

I plan to do some testing tonight. I still have my old purge valve which I replaced some months back and know is good. I will replace the current (newer) one with it and see how that goes.
Likewise, if that doesn't work, unplug it and see. I didn't have this issue until I changed the OEM PCV to the Spulen V2 Catch-can as a consequence of going APR ST2 to UM and boosting higher. The tune change has been quite the experience of chasing issues. I am curious if the check valve Spulen includes in the N80 breather hose has something to do with it. The OEMs check valve or flapper is inside the PCV housing and comparing other PCV plates, not all brands are using a check valve on the breather hose.

 

[Diggs24]

Interesting that it happened after catch can. coincidence? OP also has a CC. I don't know if he swapped back to stock or not.

 

[Mosquito]

Interesting that it happened after catch can. coincidence? OP also has a CC. I don't know if he swapped back to stock or not.

I might end up eventually going back to the OEM PCV if nothing else works and see if that does it.

I went from all 3 Stock OEM PCVs (AT, BM & BL) and stock N80 breather hose (has no check valve) to the Spulen V2+included N80 breather hose with check valve. Misfired after fuel up and initially thought it was the supplied N80 breather hose wrecking havok when I noticed it collapses under vacuum (why USP includes such cheap stuff on a $600+ catch can is shameful) so I changed it to a stock grade N80 breather hose without check valve first and days later transferred the Spulen check valve to it. It initially worked better, but it doesn't seem to be IT. Looking closer to other PCV plates, not all use a check valve on the breathe hose and I wonder if 29 PSI of boost can damage the N80 in the process or if the check valve gets in the way of proper operation. The VWR doesn't seem to use a check valve and it is probably the most used, R&D piece out there. I have a spare N80 valve, OEM PCV and hose with and without the check valve to try it with.

In the meantine, I went out to take a look during lunch and also noticed that the wiring on the N80 purge valve is a little bit brittle. Very close to the plug the cables seem slightly pinched and exposed so I got some electrical tape and tried to fix that. Noticed also that the whole cable runs pretty close to the metal valve cover reminding me of MK4 Coil Pack Harness nightmare days and while the cable is mostly shielded, the wires do run pretty bare at the plug itself. Tank is pretty full at the moment but I will try to refill on the way home and see if anything has changed before I start playing with parts again.

 

[Mosquito]

Quick update from mine.
Inconclusive so far since I have re-fueled only twice since yesterday, but only 2 gallons topping off each time and that likely equals less vapors. Still somewhat hopeful.
Since initial above post, I fixed the cabling and re-fueled 2 gallons. No real change, misfires upwards of 100+ on cyl 2 and 50+ on cyl 3 for nearly minutes at a time eventually generating a misfire code on both cylinders.
LTFTs are/were around +14%. A full fill up last time generated 250+ misfires on cylinder 2 alone over 2 minutes.

Went home swapped N80 valves and replaced breather hose with a free flowing one (no one-way check valve. Spulen and OEM PCV use a check valve, but VWR doesn't seem to use one in the fitting or hose. The VWR setup looks free flowing), cleared adaptations and drove off. LTFTs were around +14% as well. Today I re-fueled another 2 gallons during lunch and the car misfired 34 on cyl 2 & 8 on cyl 3. It then leveled off on its own in probably under 30 seconds. Never misfired again. LTFTs went down from around 14% to around 8% within a mile of leaving the gas station. It was a pleasant change.

I will have to wait and see what a full re-fuel does in a couple of days, but so far... better than before.

 

[AdrianNikonian]

I haven't been here much, had a death in the family and life changed drastically. But it goes on.

update: I have had to leave N80 aka purge valve unplugged (electrical connector), it is the only way car idles fine, runs better and it won't go crazy after a fuel up. CEL will be on but at this point I'll live w/ it.....since it is one of those gremlins that has baffled many. Ed from EQT said something about a tank pressure sensor......no idea where it is and how to go about it. That is the latest...

 

[jimlloyd40]

I haven't been here much, had a death in the family and life changed drastically. But it goes on.

update: I have had to leave N80 aka purge valve unplugged (electrical connector), it is the only way car idles fine, runs better and it won't go crazy after a fuel up. CEL will be on but at this point I'll live w/ it.....since it is one of those gremlins that has baffled many. Ed from EQT said something about a tank pressure sensor......no idea where it is and how to go about it. That is the latest...

So sorry.

 

[Diggs24]

 

[Mosquito]

Nice find. Is that Adrian's video? He wrote me some time back and he explained he did this to his car. It seems some of us have this issue where high amount of fuel vapor needs purging and it becomes a problem.

In my case I came to a conclusion of sorts as to why it happens or not that goes as follows.

The N80 valve modulates on/off in rapid succession to avoid excessive fuel vapor from leaving at once, this takes place mostly after refueling. If too much is released it usually makes cyl 2 misfire in rapid succession as that is the cylinder closest to the port. This eventually trigers a CEL. This happens less on the OEM PCV because the inner flapper restricts vacuum pull AND it is combined with oil vapors from the PCV at the same port.

PCV plates have a dedicated vacuum port and so vacuum is stronger and nearly unrestricted, only held back by the N80 modulation which doesn't appear to slow it down enough. I can usually avoid the amount of misfires by avoiding idle time right after fueling up. Sometimes I have to idle at over 1500+ rpms the first couple of minutes if caught at traffic lights or so.

At the end of the day it seems there is a mechanical balance of sorts. Too little will give you a purge flow error, too much will give you misfires. Once purge has taken place it is no longer a problem until next fuel up. E85 seems to misfire less than 93 Oct.

I have questioned in the past why the Spulen PCV valve comes with a N80 hose that collapses under vacuum. I think this may be part of the reason, besides cost. I get less misfires using theirs than a better quality non collapsing hose.

 

[AdrianNikonian]

Y

Nice find. Is that Adrian's video? He wrote me some time back and he explained he did this to his car. It seems some of us have this issue where high amount of fuel vapor needs purging and it becomes a problem.

In my case I came to a conclusion of sorts as to why it happens or not that goes as follows.

The N80 valve modulates on/off in rapid succession to avoid excessive fuel vapor from leaving at once, this takes place mostly after refueling. If too much is released it usually makes cyl 2 misfire in rapid succession as that is the cylinder closest to the port. This eventually trigers a CEL. This happens less on the OEM PCV because the inner flapper restricts vacuum pull AND it is combined with oil vapors from the PCV at the same port.

PCV plates have a dedicated vacuum port and so vacuum is stronger and nearly unrestricted, only held back by the N80 modulation which doesn't appear to slow it down enough. I can usually avoid the amount of misfires by avoiding idle time right after fueling up. Sometimes I have to idle at over 1500+ rpms the first couple of minutes if caught at traffic lights or so.

At the end of the day it seems there is a mechanical balance of sorts. Too little will give you a purge flow error, too much will give you misfires. Once purge has taken place it is no longer a problem until next fuel up. E85 seems to misfire less than 93 Oct.

I have questioned in the past why the Spulen PCV valve comes with a N80 hose that collapses under vacuum. I think this may be part of the reason, besides cost. I get less misfires using theirs than a better quality non collapsing hose.

Yep that's my first rookie video haha an impromptu one when someone asked me how to plug it etc, it worked 100% for me but that's not to say that it would on every mk7. It's been like that for almost 2 years now I believe. Yes sometimes I do get the incorrect flow code as stated on the video but that's nothing compared to what I had to deal w/ before as some here know and can read about it.

 

[AdrianNikonian]

Yep that's me alright......it may or may not work on other builds but as you know, mine was terribly affected but thank goodness I found a permanent fix!!