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Exhaust smokingfrom cold start


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Hi All:

Started to see something for the first time on my dearly beloved. When I crank her over from a cold start, the driver's side exhaust bellows out smoke for the frist 30 seconds. The passenger side exhaust doesn't do same. Any thoughts on what could be causing this? Oil level is about 1/3rd, last topped up at oil and filter change during 60k service in December. Any ideas?

Thanks,

Alf

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I suspect it's related to the cylinder bank. What am I looking at if this is the issue?

Is it blue smoke?

Is your left tail pipe coated in black soot?

How many miles have you driven since your last oil change in December?

Suggest that you check cylinder #6 and #5 plugs and report back (getting to those plugs is dead easy).

Ron

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Yes, the left tail pipe is coated in soot, though I can't say if the smoke is blue, it is grey and white. It continues until the engine is warm. The right tail pipe puts out very light exhaust, which I can describe with confidence as condensation.

Thanks, I will check the pkugs. When I had the plugs and coils changed June of last year #6 was heavily coated in soot. I also noticed crank over can be labored sometimes recently and easy others. Any thoughts would be helpful.

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Yes, the left tail pipe is coated in soot, though I can't say if the smoke is blue, it is grey and white. It continues until the engine is warm. The right tail pipe puts out very light exhaust, which I can describe with confidence as condensation.

Thanks, I will check the pkugs. When I had the plugs and coils changed June of last year #6 was heavily coated in soot. I also noticed crank over can be labored sometimes recently and easy others. Any thoughts would be helpful.

1. So, you're down about 2/3 quart of oil since December. How many miles have you driven in that time?

2. When did you first notice the problem?

3. The left exhaust pipe is "coated in soot" but the right is not, correct?

4. Are you hearing any unusual noises when you start the car or after the car is fully warmed up?

5. Have you noticed any loss of power?

6. What year car is this and what's the mileage?

7. Have you had any work done on the engine?

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Thanks for your help, my answers are in CAPS below your questions:

1. So, you're down about 2/3 quart of oil since December. How many miles have you driven in that time?

1,500 miles TOPS. I HAVE 5 MILES EACH WAY TO WORK 5 DAYS A WEEK, LONG-ISH RUN ON THE WEEKENDS, ALSO TRAVEL A BIT FOR WORK SO IT'S GARAGED THOSE TIMES.

2. When did you first notice the problem?

JANUARY, BUT IT'S GETTING WORSE. AT FIRST IT WAS A PUFF OF SMOKE, NOW IT CONTINUES UNTIL THE ENGINE IS WARM.

3. The left exhaust pipe is "coated in soot" but the right is not, correct?

CORRECT.

4. Are you hearing any unusual noises when you start the car or after the car is fully warmed up?

TAPPETS LIKE TICKING SOUNDS

5. Have you noticed any loss of power?

NOPE, BUT IT DOES SEEM TO COUGH INTERMITTENTLY AT 3,000 REVS WHEN ACCELERATING

6. What year car is this and what's the mileage?

2003 996 C4 CAB, 57,500 MILES. DECEMBER HAD THE 60,000 SERVICE DONE

7. Have you had any work done on the engine?

THE KNOCK SENSOR, 60,000 SERVICE, COILS & PLUGS AND CLUTCH HAVE ALL BEEN DONE IN THE LAST YEAR - TWO OIL CHANGESIN 2010 - MARCH AND DECEMBER. DO 5,000 MILES PER YEAR..

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Thanks for your help, my answers are in CAPS below your questions:

1. So, you're down about 2/3 quart of oil since December. How many miles have you driven in that time?

1,500 miles TOPS. I HAVE 5 MILES EACH WAY TO WORK 5 DAYS A WEEK, LONG-ISH RUN ON THE WEEKENDS, ALSO TRAVEL A BIT FOR WORK SO IT'S GARAGED THOSE TIMES.

2. When did you first notice the problem?

JANUARY, BUT IT'S GETTING WORSE. AT FIRST IT WAS A PUFF OF SMOKE, NOW IT CONTINUES UNTIL THE ENGINE IS WARM.

3. The left exhaust pipe is "coated in soot" but the right is not, correct?

CORRECT.

4. Are you hearing any unusual noises when you start the car or after the car is fully warmed up?

TAPPETS LIKE TICKING SOUNDS

5. Have you noticed any loss of power?

NOPE, BUT IT DOES SEEM TO COUGH INTERMITTENTLY AT 3,000 REVS WHEN ACCELERATING

6. What year car is this and what's the mileage?

2003 996 C4 CAB, 57,500 MILES. DECEMBER HAD THE 60,000 SERVICE DONE

7. Have you had any work done on the engine?

THE KNOCK SENSOR, 60,000 SERVICE, COILS & PLUGS AND CLUTCH HAVE ALL BEEN DONE IN THE LAST YEAR - TWO OIL CHANGESIN 2010 - MARCH AND DECEMBER. DO 5,000 MILES PER YEAR..

Well, the oil consumption is within spec (according to Porsche anyways).

Does the ticking noise go away after the engine is warmed up or is it always there?

I really think you need to pull a couple of plugs from the right bank (passenger side)....I would be looking at the #6 plug closely to see if it's oil fouled or black/sooty compared to #5.

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Thanks. What's the prognosis if it is sooty or oily?

Well, if it's just one plug that's oily, I would guess either leaking valve seals or an oil ring on that cylinder. If it's sooty, I would check the injection system (maybe the injector on that cylinder?). Assessing the plugs gives you a pretty good indicator of what's going on when you have one tailpipe a different colour than the other. Right now, we know there's something going on with the right bank and checking the plugs on that side would narrow it down even further.

When you say it "coughs" around 3000 rpm, are you mistaking that for the variocam kicking in (it changes around 3100 rpm) or did it just start "coughing" at the same time you noticed the smoke from the left tailpipe?

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If you got the sparks plug out and you see nothing specious on them, take a look with a bore-scope inside the cylinders and check for cylinder wall damage. Cylinder wall damage is a cause of ticking noise and a much darker tailpipe on one side.

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AOS (air / oil separator) can cause the smoking at startup.....

With the engine idling, try removing your oil fill cap - if its difficult to remove (because of a vacuum) then there is a good chance your AOS has failed.

If it has failed, your throttle body will be oily and need cleaning too

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AOS (air / oil separator) can cause the smoking at startup.....

With the engine idling, try removing your oil fill cap - if its difficult to remove (because of a vacuum) then there is a good chance your AOS has failed.

If it has failed, your throttle body will be oily and need cleaning too

Steve,

It's certainly worth checking but wouldn't smoke appear from both tailpipes if the AOS was faulty?

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That's very true - sorry, I was thinking of my Boxster S siamesed pipes & I didn't read the OP's first post correctly.

The exhaust system on the 996 crosses over, so if the drivers side pipe is smoking, the problem usually is from the right hand bank of cylinders....

There is a similar post on Rennlist.com titled "help - coolant in oil & smoke" on page 3 of the 996 Forum. It describes how the owner found a cracked cylinder sleeve - interesting reading - though I sincerely hope this isn't the case for Alf....

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Hi - I too had smoke at startup - not much and not for long - see video for 2 starts that show it clearly. As you can see in one start there's more smoke on the the left side, then on the other more smoke on the right. Changed the AOS and no more smoke. Maybe this helps you diagnose.

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