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

[AVCUPRA290]

I'm sure that what you are finding, ie the HP fuel pressure rail staying at a very high pressure after warmed engine is OFF is not what is meant to happen, neither is the puff of smoke at warm engine start, but, I'd think that it would cost a lot of time and money to to sort this out, also most workshops would not consider this to be an issue that is worth investigating - ie they would not be able to guarantee to resolve it.

The indirect injectors should still be spraying atomised fuel in a predetermined pattern, so not just a valve that opens and lets "some fuel" through. I've owned indirect injection cars, typically cars with Bosch K Jetronic mechanical injection where the "injectors" were just spray heads that were forced open by high-ish pressure fuel being pushed down their supply pipes, even they could give this sort of problem, and with one car one injector did, Ford dealership didn't recognise it was being a problem, but after they had bodged up another issue, I ended up demanding that this "not correct" leaking of fuel into a single cylinder was not acceptable, so I bought a single new "injector" and solved that problem quickly - then went on to getting the originally faulty injector working, these K-Jetronic injectors were just spring loaded valves that were designed to vibrate while open and by doing that they should have always been able to "self centre" and so close and seal off fuel when the supply pipe pressure dropped - this one had ended up getting stuck/located so that it could not close properly. A friend that had a Ford Escort RS Turbo bought that injector from me and it seemed to help him solve a similar issue!

Edit:- I fully understand why you are digging deeply into this, but maybe try stepping back from it and enjoy your car - though easier said than done!

Hi mate,

First thanks to this forum (you guys) for pointing out the lead of a leaky injector.

I did dig a little deeper into this problem.

I first did every check I could was to re test my brand new OEM PCV, to make sure it wasn’t sucking oil (too high vacuum). Bought a vacuum gauge and found a 2.5-2.8 inHG vacuum at the oil dip stick which is what we are looking for (PCV regulation valve is designed to open/closed at -100mbars vs ambient pressure meaning the relative crankcase pressure you should have is 2.953 inHG so I’m right into it with a cheap gauge).
I did try to rev the car with my hand underneath aeration tube and when letting off the throttle the PCV does blows vapors within the inlet so correctly functioning.
=> PCV is juste fine (thank god that’s a pricey little piece of plastic)

As shown before the valve stem seals does not look « leaky » or dirty or baked from what I’ve seen from the manifold. And I have no oil consumption nor big smokes. So I think I can rule them out too, if this is the issue it is too minor for now (and I used 5w40 for my today service instead of 0w30 so might reduce it even more).

i introduced my issue to the mechanic who performed the service on my car and he did mentioned the indirect injectors. on the last pictures Ive shown you the liquid inside the cylinder was looking like dirty petrol more than oil so I also thought about petrol coming from the manifold (this dirty) + the pictures showing black liquid deposit shown previously happened with the tank full of injector cleaners + few Seat dealers mentioned the leaky injectors as a known issue.
I did find those indirect injectors at a fair price so took 4 of them.
I bought 4 new spark plugs too.
And the oil is new.

I will keep you updated on the results on this (there is still a chance the smoke is not coming from these injectors - might be the direct ones - or might be coming from elsewhere and be indeed oil) but I’ve looked everything I could and in the end for now it is not that big of an issue !

thanks again

 

[ULIK]

Hi Mate. Did you resolved the problem? Got the same issue on my cupra. Before I removed the downpipe I saw the smoke only when warm car sitted for a while- 30 min . Now it can bee seen even on cold start (OEM downpipe out, catback on), and also when the stop is shorter- like 5 min. I checked the injectors (all 8 of them)- they were repaired (cleaned), and checked for leaks (no leaks) and after putting them back to car still a puff of smoke is observed. My car, when it does it, also idles rough for a 2-3 sek, then the smoke goes away idle is ok and everything is perfect. No smoke when driving or idle. I've replaced all those things that you did and still no luck in finding the issue. Any luck in finding the problem? I'm thinking about replacing the active carbon canister, already replaced the valve that redirects the gasoline vapours to that canister and back to engine but still problem exists. One thing more- it looks like the car does it often in spring and summer. In winter the problem seems to be smaller (only from time to time and only on warm engine after sitting for a while). The mechanics say that it's the valve steam seals but I'm not using oil almost at all (500ml for 10k kilometers). Maybe you found the solution?
Regards.
G.U.

 

[Jimbo]

Hi Mate. Did you resolved the problem? Got the same issue on my cupra. Before I removed the downpipe I saw the smoke only when warm car sitted for a while- 30 min . Now it can bee seen even on cold start (OEM downpipe out, catback on), and also when the stop is shorter- like 5 min. I checked the injectors (all 8 of them)- they were repaired (cleaned), and checked for leaks (no leaks) and after putting them back to car still a puff of smoke is observed. My car, when it does it, also idles rough for a 2-3 sek, then the smoke goes away idle is ok and everything is perfect. No smoke when driving or idle. I've replaced all those things that you did and still no luck in finding the issue. Any luck in finding the problem? I'm thinking about replacing the active carbon canister, already replaced the valve that redirects the gasoline vapours to that canister and back to engine but still problem exists. One thing more- it looks like the car does it often in spring and summer. In winter the problem seems to be smaller (only from time to time and only on warm engine after sitting for a while). The mechanics say that it's the valve steam seals but I'm not using oil almost at all (500ml for 10k kilometers). Maybe you found the solution?
Regards.
G.U.

Enough people have this issue + clears after a few seconds + is dependant on atmospheric conditions + doesn't cause any noticeable symptoms that I've just accepted it as part of the car. I also read that people with a decat experience this more which leads me to believe that it's caused partially by the cat before it's up to full operating temperature

 

[ULIK]

I think that problem is combined with to rich fuel dose on start. The car revs to about 2k rpm and when the rpm drops smoke is showing. You can't observe it when car fires up on start stop system after sitting for a while: 3-4 min, then on start it revs only at 1k rpm and the problem does not exist. Anyway l'll keep on searching because it's a pain in the ass to see smoke on start. Looks like I'm driving not a modern car but a piece of junk
Thanks for help.
G.

 

[AVCUPRA290]

I think that problem is combined with to rich fuel dose on start. The car revs to about 2k rpm and when the rpm drops smoke is showing. You can't observe it when car fires up on start stop system after sitting for a while: 3-4 min, then on start it revs only at 1k rpm and the problem does not exist. Anyway l'll keep on searching because it's a pain in the ass to see smoke on start. Looks like I'm driving not a modern car but a piece of junk
Thanks for help.
G.

Hello mate,
I agree with both of you : Jimbo is right most of cupra owners do have this and there is no other symptom aside from the puff of smoke. Ulik, yeah it’s a pain to not know why this happens and what causes this or if it is normal.
Seen some GTI owners replacing whole head under warranty for similar issue and it solves the smoke : valve stem seals. However in my case it could be small leaks from the valve steam seals but how could it not cause smokes on cold start ?
and I’ve check them with a cam they don’t look oily at all.
I’ve replaced the N80 valve (canister one), the PCV and hoses, the 8 injectors, I’m using thicker oil.. nothing changed so I gave up.
I’ve drove the car for a month back to stock (took off the R600 intake, inlet and outlet) and still got the smokes. I’ve try few days with the OEM resonator back, also got the smokes.

I agree with Jim that it looks like a rich mixture on startups that are not useful for a warm start up (ok for cold start thus no smoke). the smoke smells like petrol that’s why I replaced the injectors. Could also be a temp jauge misreading temp when you start up the car and applying a mixture for cold weather..

In the end it doesn’t seem to affect the car in anyway.
I have smoke on start up after the car sit for 30min to 6h. After a while night nothing. No rough idle just the puff of smoke on the first engine explosion, then the regular condensation of any.
Not linked to the cold start high rpm can happen with or without. Smells like petrol but can have blueish reflects.
Oil consumption is about 0,25 / 3000km but I have a small leak near the waterpump belt I have to fix, so id say the oil consumption is way in the manufacturer guidelines..
Nothing to worry about I suppose, and nothing gave me another answer

 

[ULIK]

I'm almost 100% sure that these are not valve steam seals. My car pufs smoke after it sits for more then 3 minutes or more when is hot. Not possible for a valve steam seal leak to deliver oil on pistons in such short time- that would be a big leak and car would smoke when accelerating and burn lots of oil-I have almost the same oil consumption level that you have. Anyway after I replaced the downpipe for custom one, smoke shows even on cold start but.... only when it's hot outside (hot starts smoke is still there). So if you still have OEM downpipe don't replace it or you will see smoke almost on every start
I'll keep on searching for resolution of this problem. Sooner or later something must break definitly and then the problem will be found/resolved.
Thanks for your time and for sharing that knowledge/pictures etc.
Regards

 

[AVCUPRA290]

I'm almost 100% sure that these are not valve steam seals. My car pufs smoke after it sits for more then 3 minutes or more when is hot. Not possible for a valve steam seal leak to deliver oil on pistons in such short time- that would be a big leak and car would smoke when accelerating and burn lots of oil-I have almost the same oil consumption level that you have. Anyway after I replaced the downpipe for custom one, smoke shows even on cold start but.... only when it's hot outside (hot starts smoke is still there). So if you still have OEM downpipe don't replace it or you will see smoke almost on every start
I'll keep on searching for resolution of this problem. Sooner or later something must break definitly and then the problem will be found/resolved.
Thanks for your time and for sharing that knowledge/pictures etc.
Regards

Yeah I don’t think it is either.
But it’s weird yours smoke after only 3min, I have to wait for at least 20-30min before it smokes..
but the fact you replaced your downpipe add another thing to the equation and this could just be some normal startup smoke usually filtered by the OEM cat.
If you come across any answer please share it !
no problem man

 

[ULIK]

Had the same with OEM downpipe onboard (minimum 30 min). Now 4min is enought. Carcol canister is on my mind as next to replace
I'll keep you informed if something will work

 

[The-Cupra]

Had the same with OEM downpipe onboard (minimum 30 min). Now 4min is enought. Carcol canister is on my mind as next to replace
I'll keep you informed if something will work

If you do find out what it is be sure to let us know. Mine doesnt do this so its defo not normal im on 53k miles. Curious to know, seems common.

 

[AVCUPRA290]

If you do find out what it is be sure to let us know. Mine doesnt do this so its defo not normal im on 53k miles. Curious to know, seems common.

Is your car stock ? Or do you have mods like res delete, decat, intake…

 

[ULIK]

Hi everyone. So I'm after a cyliner check with endoskopic kamera. Well it looks like the valve steam seals ..... (1 and 4 cylinder) I found some oil on the pistons and not from the injectors side. Also found some oil on spark plugs thread in 1st and 4th cylinder- don't know how it got there (the spark plugs are clean). I'm passing 130tkm so it's also time for a timing chaine check, so probably I'll be doing bouth at one time. Don't know exactly when I will repair it, the car uses only a small amount of oil, but if I do I will put a comment here about the results. Thanks for all help.
Regards.
G.

 

[AVCUPRA290]

Hi everyone. So I'm after a cyliner check with endoskopic kamera. Well it looks like the valve steam seals ..... (1 and 4 cylinder) I found some oil on the pistons and not from the injectors side. Also found some oil on spark plugs thread in 1st and 4th cylinder- don't know how it got there (the spark plugs are clean). I'm passing 130tkm so it's also time for a timing chaine check, so probably I'll be doing bouth at one time. Don't know exactly when I will repair it, the car uses only a small amount of oil, but if I do I will put a comment here about the results. Thanks for all help.
Regards.
G.

Hi, might be it then.. when you say not on the injectors side what do you mean ? On the exhaust valves side of piston head ?
If you check the previous posts on this topic, I had some deposit in all 4 cylinders but it was when my tank was full of injectors cleaner. After that only saw one cylinder with some liquid inside and thought it was fuel and it was ok for me with the fact that the smoke only appears for a limited amount of time after being parked (no smoke after one night). Finally accepted it could be either a « normal » thing for these cars, or a rich mixture on some startups leading to some un burned fuel when the engine wasn’t fully cold..
Either way I’m not consuming enough oil, and with every thing that I’ve replaced nothing changed so I’m keeping it this way, not going to pay 3000€ for those seals.

But yeah if you solve your issue please let us know !

 

[ULIK]

Yep.... directly on the exhaust side of pistons. So it can't be comming from a leaking injector. My camera was not able to show the valves from inside but still it's oil on the pistons for sure- I've touched it with camera and when I pulled it out it was oil on the end of cameras head. So it looks like the steam seals are leaking from about 50tkm when I first notice the smoke (after catback replacement). I replaced the downpipe something about 10tkm ago and that's when I've started to observe smoke even on cold start and after a short stop- 5-10 min. So yep it's time for them to be replaced. Something that I must do when I'll be inspecting timing chain. And for sure it won't cost as much as you mentioned- I've got a good mechanic . About 2 weeks ago I took my car to a mechanic that is repairing only VAG's (a true specialist but an expensive one) and he was doing a repair of Audi S3 2018 with 76tkm with almost the same issue and guess what....... valve steam seals so it's the common problem for those engines. He told me that for sure it's the seals leaking. One thing for sure. This is my last VW/SEAT/SKODA that runs on petrol. Never had such problems with diesel engines from VG group- had them few! I'm dissapointed Next car KIA STINGER GT or WRX STI - 2.0 TSI even EA888 is a technological disaster. Time for a change but first- repair and then bye bye .
Thanks again.
G.

 

[ULIK]

Hi. So I'm back from my service and they refused to change valve steam seals . They contacted 3 different services (SKODA, SEAT, VW) and in all services the main mechanic said that it can't be that issue because in 20 years history of the service they haven't done any valve steam seals replacement in this type of engine. For them it can only be carbon deposit or PCV. My PCV is new (original VW) so only carbon deposit is what's left. During injectors check mechanics also checked the carbon and a small amount of deposit was noticed so they didn't clean it (maybe it's the problem). Althout the PCV is new according to my mechanic they observed situations when a new PCV, original one, came damaged from the dealer (in one case 3rd ordered PCV valve was good-sic!). So I left it for now. Before oil change I will try to clean the carbon with sea foam or CRC valve cleaner injected in map sensor place- should help or change something if it's the problem. Probably also an oil catch tank (from BAR-TEK tuner)with tuned PCV will be instaled. It's expensive but will secure the valves from carbon so anyway it's worth to try. One way or another the issue must be solved because no one will buy a car that puffs smoke on start in normal price
Regards.
G.

 

[The-Cupra]

Hi. So I'm back from my service and they refused to change valve steam seals . They contacted 3 different services (SKODA, SEAT, VW) and in all services the main mechanic said that it can't be that issue because in 20 years history of the service they haven't done any valve steam seals replacement in this type of engine. For them it can only be carbon deposit or PCV. My PCV is new (original VW) so only carbon deposit is what's left. During injectors check mechanics also checked the carbon and a small amount of deposit was noticed so they didn't clean it (maybe it's the problem). Althout the PCV is new according to my mechanic they observed situations when a new PCV, original one, came damaged from the dealer (in one case 3rd ordered PCV valve was good-sic!). So I left it for now. Before oil change I will try to clean the carbon with sea foam or CRC valve cleaner injected in map sensor place- should help or change something if it's the problem. Probably also an oil catch tank (from BAR-TEK tuner)with tuned PCV will be instaled. It's expensive but will secure the valves from carbon so anyway it's worth to try. One way or another the issue must be solved because no one will buy a car that puffs smoke on start in normal price
Regards.
G.

whats the mileage on yours? i doubt carbon is the issue? also what year? does yours have mpi?

 

[AVCUPRA290]

whats the mileage on yours? i doubt carbon is the issue? also what year? does yours have mpi?

@The-Cupra, you said you didn’t have the issue on yours. Is it stock ECU and Stock hardware ? (Res delete, induction kit, Turbo inlet etc)

@ULIK you could try a new PCV or test your actual one. When I replaced mine the old one looked to be working perfectly fine. I’ve tested it by measuring the crankcase vacuum and seemed ok to me. Maybe it is still the source of the issue.
Not sure of the catch can to resolve it.
Also mine had the 8 injectors replaced (it has mpi) and didn’t help.

 

[The-Cupra]

@The-Cupra, you said you didn’t have the issue on yours. Is it stock ECU and Stock hardware ? (Res delete, induction kit, Turbo inlet etc)

@ULIK you could try a new PCV or test your actual one. When I replaced mine the old one looked to be working perfectly fine. I’ve tested it by measuring the crankcase vacuum and seemed ok to me. Maybe it is still the source of the issue.
Not sure of the catch can to resolve it.
Also mine had the 8 injectors replaced (it has mpi) and didn’t help.

I dont have issues on mine. Mine is at 54k now with MST V2 turbo elbow / filter and pikey mod. However this is like 90 percent motorway miles. Im wondering how yours can have carbon buildup issues. Dealership are talking rubbish.

 

[AVCUPRA290]

I dont have issues on mine. Mine is at 54k now with MST V2 turbo elbow / filter and pikey mod. However this is like 90 percent motorway miles. Im wondering how yours can have carbon buildup issues. Dealership are talking rubbish.

So no smoke on warm startup ?
stock exhaust ?

Weird, I’ve read so many people having the same issue.
No particular carbon buildup issues especially with the MPI supposed to clean the system. Just replaced the injectors thinking it could be the issue but it wasn’t.

 

[The-Cupra]

So no smoke on warm startup ?
stock exhaust ?

Weird, I’ve read so many people having the same issue.
No particular carbon buildup issues especially with the MPI supposed to clean the system. Just replaced the injectors thinking it could be the issue but it wasn’t.

nothing, not a puff. Not even if its been sat for a full week. Even if i get someone else to start it. There is no smoke all. I cant say what the issue is exactly just that i 100 percent dont have it. My cupra is the 2020 model with the dq381 and NO MPI... so i should have more carbon buildup than the earlier models. Yet no smoke ever. Its the valve cover for sure. They just dont want to do the job so they blame it on carbon.

 

[ULIK]

My car is 134k (kilometers) now (but first puff was observed at 78k when it was stock and with original exhaust system). End of 2017 with 8 injectors. Bigger turbo inlet, K&N filter and bigger pipe from filter to inlet+ catback and downpipe custom+ performance spark plugs. Was remaped with ECU and TCU now it's stock. Run on remap something about 20 then I've done backup, because one mechanic wanted to get to stock again to check parameters on VCDS-claiming that the car is overfuelled. After that he wanted to pull the engine tear him apart and search for issue- claiming finaly that it's valve steam seals (expected costs 4-5k euro). Thats not the way I wanted the probem to be solved. So the car is stock and still smoking on startup. When I was switching the PCV the old one looked ok. Last thing to replace before deassembling the motor is again the PCV (with tuned PCV and catch can) and carbon.
G.