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Lizard · Posted: Thu Apr 10, 2003 3:00 am Post subject: 931 questions

Hey guys you know how i told you that the 931 puffed smoke at idle but when friving it was fine, well it had gone away and then came back but I have abit more knowledge of it now,

it doesn't happen when the engine is at 2-3 bar on the temp guage, if the engine is cold it does happen making me think the cold start valve is leaking/faulty, the smoke isn't a true blue oil smoke and does smell like the car is running rich, and the car is not going through any oil but I am also thinking that the cat could also be part of the problem, I do have a parts car that runs perfectly so I could just drop the drive train and put it in this but it would be easier just to swap a few parts, do you guys have any other thoughts on what it could be
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3 928s,

Alex Roy · Posted: Thu Apr 10, 2003 3:14 am Post subject:

is it white (steam), blue/white (oil), or black (rich mix) smoke?

Lizard · Posted: Thu Apr 10, 2003 3:25 am Post subject:

when I first start it is more white from condesation which I dont care about, then when the smoke comes it is more of a dark blueish color, I though it could have been abit of bad gas but after topping off the tank with 94 chevron and driving around for about 4 hours I don't think that is the case anymore
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3 928s,

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

Lizard Wrote:

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

a typical scenario-
engine cold, smoke from the tailpipe = oil blowing by the valves
engine hot = oil blowing by the rings.

of course mixture problems would be the first plan of attack. take a look at your spark plugs.

-nick

Lizard · Posted: Thu Apr 10, 2003 3:34 am Post subject:

sorry about that confusion CMXXXI

the bars I was speaking of is on the temp guage there are 3 marks then the red and white boxs,

as for the cold start valve, I meant the cold start system altogether, but if I disconnect the plug on the cold start injector the car wont start on a cold start so I am alittle baffeled,
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3 928s,

Smoothie · Posted: Thu Apr 10, 2003 3:43 am Post subject:

Disconnect the cold start valve after it's running, but not warmed up and see if that has an effect on the smoke - of course this wouldn't rule out a leaky cold start valve. Another obvious possibility is that the fuel distributor is just set too rich. My car put out black smoke at idle when I first got it. I adjusted the air:fuel mix and the problem was resolved.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Lizard · Posted: Thu Apr 10, 2003 3:50 am Post subject:

- Nic the car has brank new plugs wires car and rotor on it, and it isn't an oil smoke and the car goes throguh no oil, but this weekened I will be switching over to castrol syntec 5W50, that reminds me how much more oil does the turbo take, as the NA take 5.5L of oil

as for the fuel mixture, I will be tying to set it this weekend but find it wierd that it wouldn't happen when hot if it was the air fuel mixture
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3 928s,

Smoothie · Posted: Thu Apr 10, 2003 4:00 am Post subject:

For 1982,
924 with oil filter change: 5.28 US qts. (5.0 liters)
924 without filter change: 4.75 US qts. (4.5 liters)
931 with oil filter change: 5.81 US qts. (5.5 liters)
931 without filter change: 4.75 US qts. (4.5 liters)
Of course you won't want to use US qts., so refer to the liters amounts in parenthesis.

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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Lizard · Posted: Thu Apr 10, 2003 4:04 am Post subject:

thanx smoothie
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3 928s,

Roger · Joined: 06 Jan 2003 Posts: 1235 Location: Cordova, TN

Blue smoke is definatly oil. I would guess from the turbo. Even if you dont notice the car using oil, blue smoke is oil! I would also recomend a full synthetic not a blend. The engine doesn't require it but the increased temps in the turbo can cook the oil. I belive the term is cokeing.
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1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

Lizard · Posted: Thu Apr 10, 2003 4:13 pm Post subject:

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

Some oil consumption is expected. Don't know the US spec, but I think my owners manual says 1 liter per 1,000km is normal. I don't recall ever actually using that much, but I'll toss out the trivia none-the-less.

As for expecting more smoke at higher RPM with a leaking turbo, I'm not so sure that reasoning is correct. Once you reach a certain RPM, your oil pressure pretty well levels out. The amount of oil fed to the turbo is pressure dependent, not RPM dependent (yes the pressure is RPM dependent, but for practical purposes, only to a point). So, at a given pressure, regardless of how fast your turbo is spinning, it is essentially going to get (and leak) the same amount of oil.

All this aside, I'd tend to agree, if the smoke you are seeing doesn't look or smell like oil smoke, I'd guess fuel mixture too. Since your car is new to you and you are concerned about the smoke (possibly being caused by incorrect fuel mixture), it would be a good thing to do a CIS pressure check (system & WUR) to possibly identify bad parts early on before potentially compounding problems. Preventive maintenance won't hurt anything if you do it right. Right?

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'79 Eurospec 931

john h · Posted: Fri Apr 11, 2003 11:52 am Post subject:

Lizard · Posted: Sat Apr 12, 2003 2:02 am Post subject:

thanx John I will keep that in mind, but now something else has popped up

the cars idle now jumps around, it will be running fine then all of a sudden the idle will drop then jump back up, then it will all of a sudden gain 500 rpms stay there for 10 sec and drop down again, I have adjusted the timing and doesn't help so I pulled out the volt meter and checked the coil, at the positive point on the cild the voltage is 9.80 if I rev up the car it goes up about 2 volts, and on the - pole the voltage is 6.20 again it goes up if I rev the engine, but just before the idle goes down the voltage drops about 1 volt at the coil no matter what rpm she is at, the cap and rotor are new and I checked them and they are fine, any ideas
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3 928s,