Misfire at idle

[DDale]

Hi everyone, I am new to the forum and this is my first post.

I have a 2004 mk5 gti and currently misfiring at idle, rpm looks fine but the car feels like I have a really aggressive cams (lumpy), the car drives fine without any issues except for a CEL (p0441 Evap System - Incorrect flow) that keeps coming back since owning.
I am new to the VW world and just got the car a month ago. The car is currently at 96,*** kms or near 60,*** miles, previously owned by a lady with a family. The car was healthy even though it has been sitting for 8 months.

So far I did:
Oil and filter change,
Spark Plugs - Shop replaced it with NGK PFR7S8EG
Replaced cam follower
Replaced DV Valve with GFB (I believe the previous one is factory and has a split)

Performance-wise:
Unitronic Stage1 +
Aftermarket Intake

Regarding the CEL, so far I have replaced the Charcoal Cannister and the line that comes with it, CEL came back the day after. I have now ordered the n80 Purge Valve and PCV valve to see if it will fix the p0441 code.
I tried getting more info using VCDS when the car idles rough and got misfires on all cylinders, checked it again after idles smoothed out and still getting misfire but this time only at cylinder 4.
I tried swapping ignition coils and spark plugs and still getting misfires on cylinder 4 (1 or 2 misfires on other cylinder).

Right now I'm suspecting the N80 purge valve but i read somewhere that it shouldn't cause a misfire if it fails.
I am looking for more suggestions. Thanks

[Clarkj93]

I had the same code when mine misfired, changing the purge valve made the code go away but didn't cure the misfire. I hear the pcv can cause a lumpy idly sometimes. Check the vacuum hoses as I had one split on the back of the engine passenger side that was definitely not helping:



Can try unplugging the maf on idle and checking vcds to see if it still misfires, if it doesn't then you know its an air leak somewhere between the maf and and the map sensor.

Failing that maybe get a smoke test done to find any other air leaks you can't easily diagnose?

For me it ended being a dud injector, and was similar to you in that it was only on idle.

[DDale]

I just got home and the car drove fine the whole day, no CEL and rough idle at all. Though it felt like I lost some power/hesitation (not sure if I'm just being paranoid).

I noticed the intake makes more noise, kinda like I'm making boost with just light throttle not sure if this is normal as I just installed the intake 3 days ago.

I checked VCDS as soon as I got home and got the P0441 Evap code again but no CEL. I also checked all vacuum and boost pipe, all seems okay.
I did check the maf yesterday by unplugging it while having a rough idle and it smoothed out, didn't check the misfire count though.
My plugs also looks beaten up even though its 3 weeks old, is this normal?


At this point, ill just wait till I get the new PCV and n80 Purge valve and see if it solves the problem.

[LC5F]

Just as a basic check for evap leak is to take the oil filler cap off with the engine idling - its under vacuum, should be difficult to lift off and once off, a healthy engines revs will stumble, if it's got a leak the cap will have less resistance to being lifted off and the engine will stay round about the same rough idle.
It's a good thing to do with healthy engine to experience the poor idle of an evap leak.

Yes - the P0441 is one of those codes that likes to linger, doesn't seem to make any difference to how the engine runs -
But I think you have now found out that if you replace one item it will be the other - so with the purge valve you now should be OK

[pudding]

Looks like it's running a bit rich.

Get the Evap fault sorted first and then look into possible MAF contamination from the aftermarket intake.

You always want to fix the evap faults otherwise you don't get any adaptations.  Long term fuel trims being one of them.

[DDale]

Thanks everyone for the response.

I tried the PCV check by unplugging the oil cap, it's hard to take off and the engine barely runs so I assume it's a good sign.

The sparkplugs condition might be because of the DV that I installed, I am running a GFB VTA which is a vent to atmosphere DV instead of diverting it back to the intake which might be the reason why I'm running rich.

I'll come back for an update after installing the purge valve. 

[DDale]

UPDATE!

I replaced the N80 Purge Valve and it fixed all the issues!
Car is now running healthy, drove it for few hours and no more Check Engine Light, misfire during idle is also gone. I also noticed a huge improvement in acceleration and overall responsiveness.

Here is the summary in case someone experienced this problem.

The problem
-CEL is on with P0441 Code - EVAP Emission Control Sys - Incorrect Flow - MIL ON.
-Clearing the CEL is a temporary "solution", it will keep coming back.

 

-Occasional Engine Misfire at idle, more common and worse the less fuel you have in the tank (more air in the tank).
-Noticeable loss of power/laziness during acceleration.

Troubleshooting done
-Checked n80 valve using VCDS basic test group 70 returns "EVAP Not OK"
-I tried swapping Ignition Coils and spark plugs to see if the misfire will move to a different cylinder(A common check to see if ignition coil/spark plug is the problem), nothing happened.
-Check for any leaks in the intake system and EVAP hoses, all OK.
-Checked PCV functionality. all OK.

Solution
-First replaced the Charcoal Canister but it did not fix my issue, it is a possible solution.
-Replacing the N80 Purge Valve solves all the issues mentioned above.

Thanks everyone for the help!

[mjmallia]