White puff of smoke at start only.. need your inputs !

[AVCUPRA290]

Hi,

I own a 290 cupra DSG 2016 with 86000km.

I noticed 2 days ago that on starts a puff of white smoke comes out of the exhaust immediately after the engine start.
I’ve never noticed it before but it could have been mixed with condensation since I bought this car on November and the days are juste becoming hotter.

The car is under warranty so I’m waiting Seat dealer to get back to me to book an appointment and as it will probably take at least 3 weeks before I get one I started digging by myself.

So :

- only one puff at start
- nothing if I start again after driving a bit (happens again after 15min or more.. the longer the bigger cloud)
- nothing on heavy acceleration
- idle steady
- no error code (except a catalyst one few hundred kilometers ago)
- no noticeable loss of power even if when I drove hard the car this morning it seemed to be less « kick in the ass » when accelerating as it uses to be when I think about it
- the cloud smells like gas (I think it is similar to the smell of when your start your car in the garage). Even though I’ve never smelled burnt oil I think it is recognizable.
- the car is not mapped, I only did a resonator delete and I have r600 intake + inlet + outlet.
- no oil consumption
- no coolant consumption

After reading some similar thread (a lot) :
Can’t seem to find a 100% cause of this.

1) Valve stem seals
It doesn’t smell like oil, it’s only at startup, no ticking noises, seems odd for a « young car » ?
Checked the spark plugs nothing to report, except one was smelling petrol and thus the thread was greasy with petrol.

2) PCV
Seems to work but don’t know for sure as I don’t know how to test it.
I did took off the r600 kit because I’ll go to the dealer and I noticed some oil in the inlet. Is it normal / noticeable ? I don’t know. I started the engine without the plug on the admission to see if the PCV valve might be opened and thus leaking some oil in the intake which burns at each start up.. but I felt no air coming from that pipe.


3) head gasket or other related coolant issue
No coolant consumption, no sweaty smell, no mustard in the oil

4) failing injector
Was thinking about an injector that would stay opened when engine is off and leaking a bit of petrol into the combustion chambers..
+ the petrol smell ?
Don’t know if it’s possible

5) last time I brought the car to Seat (December) they did mentioned they added 1L of oil (even though I think it wasn’t necessary). Didn’t check the level afterwards (I know I should have).
I did check it today and it still at max.
Maybe too much oil leading to burning oil ?
but why not before few days ago..

Maybe it will go away, if not I’d like to direct the seat tech on the right way when I’ll bring the car next month for servicing..

Hope some of you have some ideas !
Here is a video : How it looks like after a night

 

[The-Cupra]

Throw in some fuel system cleaner and take it for a thrashing. Try again next morning. Make sure to use good high octane fuel with additives and throw in a fuel cleaner. Iv had this issue on another car, i believe it was fuel leaking into the cylinder from what i read.

Stopped when used good fuel with a cleaner on a full tank. Next morning no smoke and never did a puff of smoke again on startup. The puff of smoke on startup is not condensation. Usually that comes a little after the cranking not straight away.

 

[RUM4MO]

I'd think that it is an injector issue, so if you tell them which cylinder you noticed the smell of petrol, that might focus them on trying a bit hard to solve this, as they will know that you have started to investigate.

 

[AVCUPRA290]

I hope it could be that simple.. I will take the car to the dealership next week for a checkup since it’s under warranty.
I’ve also discovered some serious vacuum from the oil cap when engine is running.. could it be related to my issue ? PCV failing like stuck in open/close position ?
I know some vacuum is ok but it took some force to take off the cap and the engine struggle while doing so..
Vacuum from oil cap

 

[AVCUPRA290]

I'd think that it is an injector issue, so if you tell them which cylinder you noticed the smell of petrol, that might focus them on trying a bit hard to solve this, as they will know that you have started to investigate.

Yes, I’ve wrote a list of the checks I’ve performed and my findings..

 

[RUM4MO]

Sorry but I've not tried that out on any of our newer cars - I know that I should so that I know when "things have changed" - as PCV failure!

 

[Jimbo]

Please update us once you know as I have almost identical issue although I only have slightly vacuum at oil cap so I think my Pcv is working normally. I suspect valve stem seals and I'm currently 50 miles into testing some seal conditioner. My car is only 63k miles though so again seems low for valve stem seals

 

[AVCUPRA290]

Hi,
I went to a seat dealer and they didn’t event search for the issue : « we didn’t found any electronic error code, you should put back your resonator it might come from here »
I did the resonator delete 2 months before the smoke and I can’t see how it can be related, there might be a slight loss of conterpressure but barely noticeable I think it wouldn’t create a malfunction in the engine.

Anyway, got back home and ordered a new PCV along with the hose connected to the air intake. Should install it by the end of the week.
The fact that you only have slight vacuum comfort me in the idea of replacing the PCV. I’ve also noticed some oil around the hose so it might indicate too much oil going there.


I also ordered a new upper cam timing chain cover, cam oring seals and a new oil filling cap since I noticed it was a bit greasy (might be related to the messed up vacuum in there).

I can’t help with the valve stem seals but I think you could notice oil consumption if you monitor it (whereas with bad PCV the consumption wouldn’t look abnormal).
I also noticed that when I cleaned my inlet (the oil in there) I had no more smoke even after letting the car parked for days.. with bad valve stem seals the oil wouldn’t come from there.
Also I think with valve stem seals getting bad you will experience smoke while accelerating under certain circumstances.. but maybe not when they start to go bad.. hard to find answers on this subject !

Another thing to check could be the turbo (play) and the turbo seals (I think you’d rather find oil in the outlet).

Some other cupra owners told me they have the same issue and one said it can come from the turbo conception in which some oil can stay but if it immediately goes away after start up nothing to worry about..

 

[GORDYDJ]

Hi,
I went to a seat dealer and they didn’t event search for the issue : « we didn’t found any electronic error code, you should put back your resonator it might come from here »

That just confirms what I was saying this morning. Some mechanics these days are stuck if they can't read an error code. Imagine bringing them a 1970's car with a misfire. Or smoking like yours

 

[Jimbo]

Hi,
I went to a seat dealer and they didn’t event search for the issue : « we didn’t found any electronic error code, you should put back your resonator it might come from here »
I did the resonator delete 2 months before the smoke and I can’t see how it can be related, there might be a slight loss of conterpressure but barely noticeable I think it wouldn’t create a malfunction in the engine.

Anyway, got back home and ordered a new PCV along with the hose connected to the air intake. Should install it by the end of the week.
The fact that you only have slight vacuum comfort me in the idea of replacing the PCV. I’ve also noticed some oil around the hose so it might indicate too much oil going there.
View attachment 41470

I also ordered a new upper cam timing chain cover, cam oring seals and a new oil filling cap since I noticed it was a bit greasy (might be related to the messed up vacuum in there).

I can’t help with the valve stem seals but I think you could notice oil consumption if you monitor it (whereas with bad PCV the consumption wouldn’t look abnormal).
I also noticed that when I cleaned my inlet (the oil in there) I had no more smoke even after letting the car parked for days.. with bad valve stem seals the oil wouldn’t come from there.
Also I think with valve stem seals getting bad you will experience smoke while accelerating under certain circumstances.. but maybe not when they start to go bad.. hard to find answers on this subject !

Another thing to check could be the turbo (play) and the turbo seals (I think you’d rather find oil in the outlet).

Some other cupra owners told me they have the same issue and one said it can come from the turbo conception in which some oil can stay but if it immediately goes away after start up nothing to worry about..

Nice, I'm interested to see if the new Pcv solves it for you. I think with valve stem seals they have to be really bad to smoke when idling. I might try and clean my intake then although some oil even sitting in the turbo housing is normal I believe.

 

[The-Cupra]

Hi,
I went to a seat dealer and they didn’t event search for the issue : « we didn’t found any electronic error code, you should put back your resonator it might come from here »
I did the resonator delete 2 months before the smoke and I can’t see how it can be related, there might be a slight loss of conterpressure but barely noticeable I think it wouldn’t create a malfunction in the engine.

Anyway, got back home and ordered a new PCV along with the hose connected to the air intake. Should install it by the end of the week.
The fact that you only have slight vacuum comfort me in the idea of replacing the PCV. I’ve also noticed some oil around the hose so it might indicate too much oil going there.
View attachment 41470

I also ordered a new upper cam timing chain cover, cam oring seals and a new oil filling cap since I noticed it was a bit greasy (might be related to the messed up vacuum in there).

I can’t help with the valve stem seals but I think you could notice oil consumption if you monitor it (whereas with bad PCV the consumption wouldn’t look abnormal).
I also noticed that when I cleaned my inlet (the oil in there) I had no more smoke even after letting the car parked for days.. with bad valve stem seals the oil wouldn’t come from there.
Also I think with valve stem seals getting bad you will experience smoke while accelerating under certain circumstances.. but maybe not when they start to go bad.. hard to find answers on this subject !

Another thing to check could be the turbo (play) and the turbo seals (I think you’d rather find oil in the outlet).

Some other cupra owners told me they have the same issue and one said it can come from the turbo conception in which some oil can stay but if it immediately goes away after start up nothing to worry about..

any updates? New pcv fitted?

 

[AVCUPRA290]

any updates? New pcv fitted?

Hi, new PCV just fitted, same amount of vacuum as before and other cupra owners did confirm they do have the same negative pressure at idle..

Don’t know yet for the smoke I’ll drive it tomorrow and let you know.

But after cleaning the oil in the intake & putting back the OEM air box (I had r600 box, pipe, inlet, outlet without remap) I’ve never had again the same smoke I’ve shared on the video..
Only little puff of startup that doesn’t seem alarming at all.

 

[The-Cupra]

Hi, new PCV just fitted, same amount of vacuum as before and other cupra owners did confirm they do have the same negative pressure at idle..

Don’t know yet for the smoke I’ll drive it tomorrow and let you know.

But after cleaning the oil in the intake & putting back the OEM air box (I had r600 box, pipe, inlet, outlet without remap) I’ve never had again the same smoke I’ve shared on the video..
Only little puff of startup that doesn’t seem alarming at all. View attachment 41564
View attachment 41565

Very intresting, i wonder why the r600 intake would cause smoking? Did you take the car off the battery when you changed the intakes back to stock? Just trying to figure out why this might be. Let us know how you get on with the smoke.

 

[AVCUPRA290]

Very intresting, i wonder why the r600 intake would cause smoking? Did you take the car off the battery when you changed the intakes back to stock? Just trying to figure out why this might be. Let us know how you get on with the smoke.

I don’t know maybe messing with the air/petrol mixture ? Or pulling way much air than the OEM thus impacting PCV function ? Really don’t know mate, maybe it’s not even related..
And no I didn’t disconnect the battery, why ?

 

[AVCUPRA290]

Hello,

No smoke at start up today morning and the car seems to run well (better).
The idle before replacement was 750rpm and is now 700rpm don’t know if it’s related.
I did drive the car hard today and the power was back but I did noticed a bit of smoke at start up this evening.

Ive also replaced some other parts you can read it Here

I did noticed some oil under the car around the rear main seal and the purge cap on the oil pan.. this oil wasn’t there before all these problems. It could have been related to a messed up pressure in the crankcase and thus the PCV ?
I’ve cleaned it and will monitor it along with the smokes.

 

[The-Cupra]

Hello,

No smoke at start up today morning and the car seems to run well (better).
The idle before replacement was 750rpm and is now 700rpm don’t know if it’s related.
I did drive the car hard today and the power was back but I did noticed a bit of smoke at start up this evening.

Ive also replaced some other parts you can read it Here

I did noticed some oil under the car around the rear main seal and the purge cap on the oil pan.. this oil wasn’t there before all these problems. It could have been related to a messed up pressure in the crankcase and thus the PCV ?
I’ve cleaned it and will monitor it along with the smokes.
View attachment 41609
View attachment 41610

I believe the rear main seal leaking oil is due to a bad PCV (causing too much pressure). Iv seen this mentioned a few times. What mileage is your car? Has it ever been tuned? Tuning it can giving the PCV a harder time and therefore need to be replaced sooner.

Your best bet is it leave the car 24 hours and then monitor it on a cold startup.

Fingers crossed its ok, keep us upto date! Im going to replace the PCV on mine too!

 

[AVCUPRA290]

I believe the rear main seal leaking oil is due to a bad PCV (causing too much pressure). Iv seen this mentioned a few times. What mileage is your car? Has it ever been tuned? Tuning it can giving the PCV a harder time and therefore need to be replaced sooner.

Your best bet is it leave the car 24 hours and then monitor it on a cold startup.

Fingers crossed its ok, keep us upto date! Im going to replace the PCV on mine too!

Yes I’ve seen it too !
the car has almost 87000km and I believe was never tuned since it was under seat service plan before I bought it. I did install r600 admission kit (with inlet and outlet) though without remapping it as mentioned. I took it off & will put it back for remap if I do it one day.

Yes I will monitor the smoke on my everyday use of the car, now that I’ve started using it again.
& I did have some smoke at startup after a hard drive in the mountains.

Some cupra owners mentioned having this type of smoke for a long time but everything is fine so I will see if it gets worse or if seals are leaking or other symptoms !

 

[The-Cupra]

Yes I’ve seen it too !
the car has almost 87000km and I believe was never tuned since it was under seat service plan before I bought it. I did install r600 admission kit (with inlet and outlet) though without remapping it as mentioned. I took it off & will put it back for remap if I do it one day.

Yes I will monitor the smoke on my everyday use of the car, now that I’ve started using it again.
& I did have some smoke at startup after a hard drive in the mountains.

Some cupra owners mentioned having this type of smoke for a long time but everything is fine so I will see if it gets worse or if seals are leaking or other symptoms !

54000 miles (87000km) is low milage. I wouldnt expect the PCV to fail by then. Iv seen people say 60k miles is a good place to replace it. Ill be doing mine next week.

 

[AVCUPRA290]

Yes and the car is in a really good state from what I’ve seen so far..
anyway I did replace it in case smoke was coming from it failing..
Don’t know if the old one had failed, I was able to blow through it when removed but didn’t try on the new one before putting it in..

 

[AVCUPRA290]

Could be great to have more feedbacks from other cupra owners.. if they have or not some smoke at startup sometimes