Rough idle, specially when starting the car

[Shachar85]

Hi all
2012 Leon 1.8t, 7dsg. stock.

When I start my car it idle very rough for the first 30 seconds or so.
After that it feels like something is "released". The rpm seems stable, idle is still a bit rough, but not like before.

I changed the spark plugs (needed changing anyway), air filter is new, changed oil recently.
The car did 90k km.

Any ideas what to check?

 

[Legojon]

You checked the PCV for leaks? There's a gasket inside it which sometimes wears causing idle issues.

 

[Shachar85]

No I wasn't aware of that issue.
How do I check it? Just by looking for leaks?

 

[Legojon]

It's this thing that looks like the starship enterprise and the pipework around it. Have a look see if you can see a light misting of oil around it. Also, pull the dipstick out and check it still has it's rubber o-ring on. These tend to split and fall off and creates a vacuum leak.

 

[Legojon]

 

[Shachar85]

That's a useful video! I'll check it later today.

I took some photos. It looks like something is leaking. I'm not sure i see the source.

 

[Legojon]

I can't quite tell if that's a greasy fingerprint on the pcv hose or a leak lol. But.. what I would recommend to start with is get some degreaser and a rag and clean the lot up! That'll make it easier to see whats leaking and whats residual oil. Not sure on that particular model, but on mine you can take a couple of screws out and take the lid off the pcv, allowing you to inspect the gasket and the internal passageways.

 

[Shachar85]

Ok i did that test. When I pull the oil cap, it is getting sucked back. If I take it out for half a second the engine chocke.

If I understood correctly from the video - this vacuum feeling when I pull the cap - is bad? Does it mean the membrane is torn?

 

[Legojon]

The PCV is about the same price as a set of decent spark plugs and is really easy to change (just a handful of screws and the pipe to clip off). I think it's worth giving it a try to see if it solves the issue. If you want to be 100% sure, unclip the pcv hose by squeezing the clip and see if its full of oil. Then do the same for the actual pcv, remove it and inspect it for oil. But for the price, if your taking it off, would be worth putting a new one back on anyway. Seat did several revisions of it anyway. so if its the factory original chances are there's a later version anyway.

 

[Shachar85]

The PCV is about the same price as a set of decent spark plugs and is really easy to change (just a handful of screws and the pipe to clip off). I think it's worth giving it a try to see if it solves the issue. If you want to be 100% sure, unclip the pcv hose by squeezing the clip and see if its full of oil. Then do the same for the actual pcv, remove it and inspect it for oil. But for the price, if your taking it off, would be worth putting a new one back on anyway. Seat did several revisions of it anyway. so if its the factory original chances are there's a later version anyway.

Not really. Here in Israel this part cost 304 usd.
I will have to buy a chinese part (30usd) or buy the
917-064 Dorman PCV Diaphragm for about 20-25usd.

The breather is indeed with oil inside. Does it mean the membrane is torn? (I'm not sure exactly how the pcv works, but I understand no oil should be there)
I cleaned a bit to see if the pcv also leak oil.

 

[Legojon]

Pcv is a one way valve. It uses vacuum pressure to take combustion gases and recycle them back into the intake manifold. Hence if it fails you create a vacuum leak. On your model can you remove the top off the pcv to inspect inside or is it sealed? And yeah, shouldn't have oil dripping out of it.

 

[Shachar85]

I tried removing the top. It is clipped. You can see it in the second picture in my previous post.
Probably 50% that I'll break it while trying.

Btw, after googling, trying to understand this PCV bettter, I realized that this cause an oil leak in another place as well.

Which is great news because I was afraid that the turbo is leaking oil. It seems that oil from the PCV get there.

Thanks so much for all the information!
I will buy the Dorman repair kit. About 40$ after shipping and it seems it will fix the problem.

 

[Legojon]

No worries. I hope it sorts it out for you. Let us know how you get on.

 

[Shachar85]

Ok, some bad nrwsin that matter.
I replaced the diaphragm. The old one had a small tear. I was sure this is gonna fix it. But nothing changed. Same rough idle when I start het car.

I noticed there is still oil in the pipe going tou from thr pcv unit. I attached (an older) picture to explain which pipe.
And I wonder if oil can get there fron somewhere else. Or maybe the diaphragm I put is bad one...and already torn? Not likely

 

[Shachar85]

Someone? Any idea?