Yeah, especially when it’s the daily/only car 
Injectors were last touched in 2016. As I recall 4 were replaced and the other 6 were refurbished with new filters and grommets. But I can’t remember what kind.
Is the PCV the same as the oil separator, or a different part? The oil separator was just replaced. But I still feel like there must be a leak somewhere in the system. Just not sure how to get it checked out. (Language problem, I need French or Dutch)
Bonjour Mixofia.
Je suppose donc que tu es du côté de la Belgique. La pcv est effectivement le séparateur air-huile, boîtier noir repris par deux torx à l’arrière du collecteur d’admission. Si tu veux voir s’il y a une fuite, c’est machine à fumée obligatoire à mon sens.
Hi Mixofia,
I supposed the you’re located in Belgium then.
The pcv is the same as the oil separator, held by two torx screws on the rear side of the intake manifold.
If you’d like to locate any supposed leak, the use of a smoke machine seems necessary.
Oui monsieur, mais je parle seul un peu français.
I have already replaced the oil separator. But I need a smoke test—comment-je parle « smoke test » en français?
« Je veut voir s’il y a une fuite du vacuum. Est-ce que vous pouvez ça faire avec une machine à fumée? »
[UPDATE] I found a vacuum leak(!) In the end, I couldn’t find a garage to do a smoke test, so I made a DIY smoke machine, and voila!
See this post for more details: What are the 2 hoses that connect to the pass air intake hose?
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Check the PCV system. The vac hose that goes from one bank to the other. I chased the same issue for a while. It’s the thick plastic with braided mesh around it. $200 dealer part but it smoothed everything out. Pull that hose and look for cracks.
Make a DIY smoke machine, it’s gonna save you a lot of time guessing at where the leak is. see: What are the 2 hoses that connect to the pass air intake hose?
Update: after 3 months of no significant misfires or CELs the #6 problem came back. Plugged in Vag com and was following the O2 levels indicating I’m running a bit rich on Bank 3.
Any ideas what It could be? Again mostly on coldstarts sometimes on red light stops but very sporadic. Injectors are all new.
Could you post your fuel trims from group 032 for both ECUs? Maybe they’ll reveal something
I have one for block 033 which said negative 12-17%. But LTFT are around 3-5% sometimes 7%
In that case I would clear them, and wait until car adapts with new ones, and see what they’ll turn out to be
Uploading: 20220403_093602.jpg…
Tried it, even resetted the entire ECU didn’t change much still only #6 very randomly
Been chasing that issue for 2 years now and I’ve started to build a brand new engine already because I got sick of it
These short term fuel trims look not too great tbh. Did you just clear codes? Also, how much oil do you burn between oil changes?
Don’t burn any oil. I lose oil (massive leak) but not really a burning issue. Compression is good at 10,5 Bar and there aren’t any scratches on the cylinder walls. Just some black dots but these are also present on every other cylinder.
Honestly there are not that many possibilities left. In my opinion they are the following:
-faulty ECUs
-faulty wiring
-faulty injectors (i know they were replaced, but still, shit happens)
-wrong injectors (do you have any pictures or product code for ones you have used?)
Also check your fuel rail pressure at hot engine (oil temp above 80 celcius) at group 140 field 3. After shutting down hot engine it should rise considerably, even up to 100 bar and above. If it stays still or drops than that could indicate leaking injector.
I have heard some people saying that hitachi injectors without VW stamps would not keep their parameters.
I used the genuine Hitachi ones. Thing is that before the injector change it also was number 6 only so either i have some really bad luck or it’s not the injectors. I should do 140 this week I once tried 141 and it was something like -0.10 which doesn’t make any sense but yeah. Maybe I should check the harness? Don’t know. Slightly reving the warm engine smoothens it out.
Injector harnesses do indeed loose their insulation due to contact with oil combined with high temps. I just recently changed my injectors and I did repair mine. So I’d say it is really possible that you have either stripped insulation on your wires to this injector, or even broken clip on that particular injector connector.
Update: after exactly 5 weeks of running buttery smooth the engine now threw a CEL for cylinder 6 sporadic misfire. It is really hard to believe that the engine is faulty since the intervals between CELs are getting longer and longer. It really does the usual injector fault symptoms like a popping sound from the left exhaust pipes. Is it possible that an injector can fail from day one?