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A puff of smoke when I start up

The past 2 or 3 times I've started my '79 SC it is puffing white smoke that smells like burnt oil and lasts for a brief second, its a bug puff that makes a little cloud behind the car, gone in a few seconds.
Something tells me this cant be good, what do you think it is?
Old 08-06-2009, 09:20 PM
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Mine does it after sitting for long periods (weeks).

Have you checked your oil level lately?

Any oil pooling in the intake?
Old 08-06-2009, 09:23 PM
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There is a drip onto the exhaust manifold. The oil level is right on, just above the lower mark. I had my girlfriend stand behind the car to tell me if it was coming out of the exhaust pipe or from the bottom of the engine. Its coming out of the exhaust pipe.

Last edited by white99c2; 08-06-2009 at 09:50 PM..
Old 08-06-2009, 09:36 PM
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This started today

I've not driven the car today but have had to pull it in and out of the garage 3 times and each time I started it -- it smoked. Could it be these couple of quick starts and shut down have left to much oil in the sump? I just read that I should let it idle a minute to return oil to the tank, correct?
Old 08-06-2009, 09:48 PM
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Sure it isn't fuel instead of oil? I thought oil was more blue-ish in color.

Does it smell like sulfur at all?
Old 08-07-2009, 04:16 AM
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+1 Sounds like a fuel issue not an oil issue - the hot weather could be a factor with your CIS.
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Old 08-07-2009, 04:37 AM
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Mine too. Sometimes worse when the car is parked on a slope.

I believe this is what happens.

There is oil around the valve train. If on a slope a small amount of oil will travel down the valve stem, past the valve guide, into the intake or exhaust manifold. Some small amount may enter the cylinder. The smoke you see on start up is this oil. A properly working catalytic converter will remove this smoke.

I would not consider this a problem unless the smoke is excessive and continues while running. Then some examination should be done.
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Old 08-07-2009, 06:12 AM
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If it is fuel, maybe your mixture is a little rich or your cold control pressure is too low, giving you a too rich mix @ startup. Or maybe your CSV is firing a little longer than it needs to.
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Old 08-07-2009, 07:30 AM
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I just thought it was part of the charm of these 911s. Mine sometimes makes a big poof of white smoke at start up, but that's if it doesn't start right away, and I've been messing with it for a few extra cranks. I think it's just extra gas burning off.

But I did hear a little back-fire once back there! And yes, I do have a pop-off valve on the airbox.

So Rob, does yours have the pop-off valve?
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Old 08-07-2009, 07:31 AM
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911SCs aren't called "Puff the Magic Dragon" for nothing. . .
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Old 08-07-2009, 07:45 AM
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Yes I have a pop off valve - it smells like oil to me maybe sulfur. BTW my car has a car bypass pipe on it, NO CAT.

I'm taking it out for a ride and when I get back I'm going to let it idle for 30 seconds before turning her off. I want to see if that helps and prevents the poof next time I start up.
Old 08-07-2009, 08:23 AM
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My 1973.5T without a cat. or any emission stuff occasionally gives off a puff of smoke on start-up. In fact so did my 1974 911 and 1979SC. The engines in all three cars were not worn, valve guides were good and no issues or concerns. I think for my 73.5 it might be the oil-squirters. Whatever, its only on start up and just one of those Porsche 911 characteristics, but worn valve guides can always suspect.

I have noted that sometimes adding too much oil allows a backflow into the airbox through the breather when the level goes up in the oil tank. I have always heard that you should keep the level on the dipstick about half on the mark when the engine is hot. Take a look in the airbox and see if you have any oil accumulating toward the rear of the box.

But you said, "White smoke". Thats weird. Maybe the radiator is leaking?!

Bob
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Old 08-07-2009, 08:26 AM
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Mine does this in the morning. I always thought this was a characteristic of the boxer engine. The cylinders are horizontal, so after shut down whatever oil was inside the pistons/rings would slowly seep out and pool along the bottom of the cylinder. It only happens if the car has been sitting for several hours. At start-up the oil ignites and creates a cloud of smoke. This cannot happen if the cylinders are not horizontal as the oil would simply drain out.

That's my story and I'm sticking with it.
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Old 08-07-2009, 11:35 AM
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White smoke is oil while black smoke would be excessive fuel.

Radial engines burn lots of oil on startup:
http://www.flightlevel350.com/Aircraft_North_American_B-25_Mitchell-Airline_Private_Aviation_Video-9654.html

Migs tend to run rich:
http://www.flightlevel350.com/Aircraft_Mikoyan-Gurevich_MiG-29-Airline_Russia_-_Air_Force_Aviation_Video-14730.html

Last edited by stlrj; 08-07-2009 at 12:06 PM..
Old 08-07-2009, 12:04 PM
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I get a puff of smoke (oil) at start up. Much, much more noticeable after the car has been sitting for a long time. Engine is a 2.2 w/carbs.

That being said, I'll be looking at redoing the top end because I know my valve guides are getting worn (smoke on decel).

I've read elsewhere in this forum that a puff of smoke on startup is common and not a big deal.
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Old 08-07-2009, 12:18 PM
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mine (75 w/ 79 mostly stock engine) does the same thing, especially when "overnight" cold. Never lasts for more than a second. I figured its hot/thin oil that creeped past a seal as the engine cooled (tolerances opening), before the oil thickened up.

Also, SCs run "very" rich right at startup - between the cold start valve and the WUR adjusting the control pressure you have a lot of fuel in there.

Either way, I wouldn't worry about it too much. Now, if the smoking doesn't go away, then you might have a problem.
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Old 08-07-2009, 12:21 PM
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The puff of smoke is normal. It even does it on the 2009's. It's b/c of the horizontally apposed engines. Oil will fill the bottom of the case, and creep past the piston rings. It is more noticeable when you leave the car on an incline, or if it has sat for a long period of time.
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Old 08-07-2009, 03:58 PM
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[Welcome to the Boxer motor design. Totally normal as long as its only on startup and goes away quickly. Otherwise you may have to look into it further.
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Old 08-07-2009, 05:28 PM
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my 73.5 does it also, no noticeable oil consumption
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Old 08-07-2009, 06:50 PM
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No Pcar expert here, but on most cars for engine wear you look at two things for smoke out of the exhaust. 1) smoke on acceleration=rings, 2) smoke on deceleration = valve guides. My 84 gives a puff of white smoke out the exhaust if it's been sitting for weeks.
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Old 08-07-2009, 08:36 PM
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