997 C4S Intermittant Smoke on startup
Discussion
I'm wondering if anyone can help here. My housemate has a two year old 911 C4S PDK Cabriolet (which I also drive quite a lot) and it has developed an issue whereby sometimes upon start-up it smokes badly for 10-20 seconds. I'm not talking a little smoke, I'm talking a huge cloud. We have been trying to figure out a pattern to when it does this but there is nothing too conclusive other than it is most common when the cars last journey was a short one (though sometimes does it when last journey was a long run too) and seems to happen more when the car has been parked on a camber - not necessarily and extreme camber. Has anyone else seen this? The car will be going into Porsche to be looked at and is still under the original warranty, but I was just wondering if anyone could give a heads-up on what it may be.
On a totally unrelated point, does anyone know if it is possible to set the car to leave the windows down when you lower the roof as every time the roof come down it puts the windows up and then I immediately have to put them back down which seems pointless.
Thanks in advance.
On a totally unrelated point, does anyone know if it is possible to set the car to leave the windows down when you lower the roof as every time the roof come down it puts the windows up and then I immediately have to put them back down which seems pointless.
Thanks in advance.
Occasional smoke on start up is perfectly normal, however 10-20 seconds sounds excessive. If the car is actually 'blowing' smoke for that length of time than I would get it checked out.
A 2-3 second puff of smoke which may take 10-20 seconds to clear is usually fine, although a way to prevent it is let the car idle a few seconds before shutdown.
A 2-3 second puff of smoke which may take 10-20 seconds to clear is usually fine, although a way to prevent it is let the car idle a few seconds before shutdown.
Have you checked the oil level? Mine had something similar (gen2 manual not PDK) and it turned out to be a misaligned piston ring allowing more oil than necessary in to the cylinder. A symptom was significant oil usage. They rebuilt the engine as a precaution (initial diagnosis was bore scoring and Porsche GmbH panicked!).
I imagine, as it's under warranty (and PDK so no potential over rev issue) that this'll be sorted pretty quickly.
I imagine, as it's under warranty (and PDK so no potential over rev issue) that this'll be sorted pretty quickly.
MrTickle said:
Occasional smoke on start up is perfectly normal, however 10-20 seconds sounds excessive. If the car is actually 'blowing' smoke for that length of time than I would get it checked out.
A 2-3 second puff of smoke which may take 10-20 seconds to clear is usually fine, although a way to prevent it is let the car idle a few seconds before shutdown.
+ 1.A 2-3 second puff of smoke which may take 10-20 seconds to clear is usually fine, although a way to prevent it is let the car idle a few seconds before shutdown.
May also be a sign that the Air Oil Separator (AOS) is on the way out (this was a common problem with the Boxster and I assume the AOS is similar on the 997).
Yeah, I have checked the oil level a good few times and it doesn't seem to be going down significantly (certainly well within what Porsche suggest oil usage may be). At about 6500 miles since it's last service it's one notch above the middle on the digital readout. We've tried letting the car idle for a minute after parking but it's still done it after that. I'll try and get a picture next time it does it, but it's smoking to the point where everyone does tend to be looking at you as if your cars about to go up in flames which isn't particularly cool. I'll also try and examine more closely the amount of time the smoke is actually blowing for as I may be overstating it by the time it is taking to clear.
markyboy911 said:
When mine did this, it turned out to be a leak in the header tank and coolant was dropping onto exhaust and burning off on start up. Tank replaced - job done.
Check coolant levels to be safe as the system is pressurised and a leak may also be coming from elsewhere.
Worth a try.
HTH
Thanks, I'll check this when I pick up the car (at the detailers for it's winter 'protection' detail).Check coolant levels to be safe as the system is pressurised and a leak may also be coming from elsewhere.
Worth a try.
HTH
Does letting the car idle before turning off work on the 997 GT3 as well, I find this trait of the car quite annoying and if it is this simple bingo! What do we call a few seconds? I can't imagine I pull into the garage and turn off immediately so how long should I give the old girl to settle down?
I doubt it Andy, certainly makes no difference to my 996 GT3.
The last couple of miles of my journey are always spent lightly cruising and then the car idles a little once I'm in the garage.
Some start ups are clear, some cause a puff of smoke. I don't like it either but every 911 I've owned has done it. It's just what they do.
The last couple of miles of my journey are always spent lightly cruising and then the car idles a little once I'm in the garage.
Some start ups are clear, some cause a puff of smoke. I don't like it either but every 911 I've owned has done it. It's just what they do.
AndyBrew said:
Does letting the car idle before turning off work on the 997 GT3 as well, I find this trait of the car quite annoying and if it is this simple bingo! What do we call a few seconds? I can't imagine I pull into the garage and turn off immediately so how long should I give the old girl to settle down?
Before shutting off the engine, I idle both engines of my cars.In the case of the Turbo the owners manual calls out a 2 minute idle time prior to engine shut down to give the engine/turbos time to shed some heat.
Oh, how long do I let the engines idle (except those times I adhere to that 2 minute guideline)?
Well, from just a few seconds, 5 to maybe (maybe) 10 seconds, to under 30 seconds. That is unless the engine's been working hard. But I always try to drive the car easy after pushing the engine (and the car) hard to give the car and the engine the street equivalent of a "cool down lap" before I shut off the engine.
Since I almost always let the engines idle, though maybe not always for 2 minutes in the case of the Turbo, I can't say if it helps cut down on the smoking. I've even tried going the other way, tried raising RPMs to say 1500 for a few seconds prior to shutting the engine off and the times I've done this the results have been inconclusive. The engine didn't smoke a few times then the next time I started the engine after doing this it did smoke. But it doesn't smoke every time. Nor does it never smoke. To me it makes no difference.
The real problem is the AOS sucks and routes too much oil vapor to the intake where the vapor contacts the intake walls and reverts to liquid oil again. Once the engine is shut off the heat soak gets to the intake and the oil then warmed up drains down into a combustion chamber if the intake valves are open or collects on top of the valves if the valves are closed.
The next time the engine is started the oil of course is burned and in the few initial combustion cycles because the engine is cold the converters are cold the oil causes the smoking.
Up to you. I still like to let the engine idle a moment or two before shutting the engine off, longer if I've been pushing the engine. But I'd not go overboard with this idling business.
Remember the guidelines regarding this smoking upon start up is as long as the smoking is short lived, the engine doesn't exhibit any other symptoms, the CEL stays dark, you can ignore the smoking.
Interesting stuff. I've tried letting the car idle for a minute before it's turned off but it seems to make no difference. I do usually let cars idle (and drive them gently for a bit) after a good hard run - I was recommended to do this in the Impreza to keep the turbo happy. Ah well, will try and get more detail on how long it smokes for and I'll check the coolant tank too.
Hi my boyfriend has got a 997 Porsche cab manual and has experienced big clouds of smoke on startup. It has has happened after short and long journeys. It lasts for 10 to 20 seconds. Dealer is asking for video evidence which we find ridiculous. Can anyone help or advise it is under warranty what should we do.
I am no worrying you that this is bore scoring - however we have been doing a lot of development work on the causes etc and while doing this have fitted different pistons from different manufacturers with different coatings and we did find that if the car is parked on a slope it often made a difference to the amount of smoke on start-up and how long it lasted.
Although our findings about pistons tapers, and the position and size of ring lubrication holes etc - all had an influence - it would suggest that in cases of bore scoring the oil can run into the bore via the scored area and smoke on start-up.
So I would get two things checked - first an experienced viewer of a boroscope to inspect the cylinder bores and then - if that is OK and it is parked on a slope - try it the other way around and see if it makes any difference - and if so there may be a simple solution.
If it is parked level - a failed AOS can also create this problem but then usually also would if left ticking over and then driving off.
Bax
Although our findings about pistons tapers, and the position and size of ring lubrication holes etc - all had an influence - it would suggest that in cases of bore scoring the oil can run into the bore via the scored area and smoke on start-up.
So I would get two things checked - first an experienced viewer of a boroscope to inspect the cylinder bores and then - if that is OK and it is parked on a slope - try it the other way around and see if it makes any difference - and if so there may be a simple solution.
If it is parked level - a failed AOS can also create this problem but then usually also would if left ticking over and then driving off.
Bax
Thanks for your reply Bax the car is always parked on a drive which is slopped and engine being at back is at top of slope.
This has happened thought not from driving away after being parked, but when car has been 5 to 10 miles parked on flat for an hour and then happened on startup ? Would this cause the same problem ?
Thanks
This has happened thought not from driving away after being parked, but when car has been 5 to 10 miles parked on flat for an hour and then happened on startup ? Would this cause the same problem ?
Thanks
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