Puff of smoke on startup

[Shoppinit]

I noticed this a couple of times recently.

Sometimes when I start the car, I get a puff of gray / black smoke from the exhausts as the engine fires up. I'm not sure if it's both sides or just one.

I have a feeling that it might be an excess of fuel due to me having started the engine just previously to move the car out the garage, but I need to do some more testing.

Anyone have anything similar?

[Gravitypilot]

i think i do also from cold...

[JCviggen]

Well if it's not blue but gray and a seriously noticable amount that must mean you get some fuel in the intake during rest. Usually a leaking injector that seeps fuel until the fuel pressure drops (nothing else that can deliver fuel there) . I do not think it is normal, but on the other hand it's nothing to panick about either, it's only a little richer on startup then.

[posterboyj]

grey or black indicates over fuelling - blue is burning oil. I would use Vagcom to check the health of the pre & post lambda and block 031 for fuel trims

[drybeer]

I get a similar thing but NOT every cold start. Mostly it's when I've started the car to reverse out of the garage, washed it and then simply put it away again. If the car has had a run then I don't get anything.

Would oil in the cylinder liners not cause a little of this also?

My 911s used to give a puff of smoke also when not started for a few weeks - but I put this down to the flat engine and oil lying in the bores. Don't know if it's at all possible in a V8?

[JCviggen]

I would use vagcom to check the health of the pre & post lambda and block 031 for fuel trims

I do not suspect he'd find anything meaningful there. On startup neither lambda is active because they need to warm up first. Startup is a pre-determined amount of fuel that I do believe has a correction factor based on what the ECU sees in normal closed loop running but then it would have to run like crap which is obviously not the case.

It has to be some fuel that seeps into the intake after the engine has been turned off. If it only does this after standing still a good period of time (so not when restarting it right away) then you've found the most likely problem.

[Shoppinit]

Bumping this back up.

I reckon my startup puffs are oil burning. They are definitely blueish / white. Only last for about a second.

Same amount of smoke from both sides.

Not many places where oil could get in to the cylinders in such small quantities. I'm thinking valve stem seals.

Anyone have any ideas?

[mavada]

On cold engine starts, especially, the ECU will momentarily run a rich mixture to get ignition going, then thin it back to normal once the O2 sensor can get an accurate reading. The puff of 'smoke' probably has a sweet smell and would contain a small amount of poorly combusted fuel, some uncatalyzed exhaust, and likely a bit of condensation.

You see the same thing with worn or damaged valve guide seals. The way to tell the difference is to let the car sit overnight, then inspect the inside of the cylinders (through the spark plug hole) using a bore-scope. If there's oil, it's valve seals. If it's clean, it's turbo seals.

[Shoppinit]

Thanks for that copy / paste from the saab forum.

As I said above, the smoke is blueish, so it's not overrich mixture. Don't think it's the turbo seals because of the distance from the turbos to the inlet and the fact that the smoke is only for a very brief duration. I discounted oil accumulation in the intercoolers for the same reason, although I cuold be wrong about that; I might drain them to see. Because they are not made of swiss cheese like the OE ones then the oil has nowhere to escape to.

I don't think I'm going to worry about it until it gets worse. If it does. Was just wondering if other's did it and I find it odd that I have *never* heard of a problem with valve stem seals on the RS6.

[mavada]

yeah, you came across that post too. I thought it might have a explanation to your possible trouble...

[Shoppinit]

It's not a bad explanation. I just don't think that you would see such small quantities of oil using an endoscope. Not that I have one, and I certainly can't be bothered to go to the faff of pulling plugs out.

[el_ringo]

Im sure I get a tad of blue when I start it cold after being sat a few days. It is not nearly as much as the wifes old boxster used to chuck out. Ill go start it now and look again....

[el_ringo]

None this time, I even started it twice to test moving it out. I will have to see when it does it again.

[vikingrs6]

Bumping this back up.

I reckon my startup puffs are oil burning. They are definitely blueish / white. Only last for about a second.

Same amount of smoke from both sides.

Not many places where oil could get in to the cylinders in such small quantities. I'm thinking valve stem seals.

Anyone have any ideas?

Hi Shoppinit, I had a similar issue.. check this out http://forum.rs246.com/viewtopic.php?f=2&t=82851 and http://www.rs6.com/showthread.php/20472 ... highlight=

[Shoppinit]

I remember those posts. How was the oil getting into the cylinders? Throught the sparkplugs? How come you had smoke coming from both sides though, but managed to fix it with one rocker cover gasket?