25 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHSmoke from left exhaust pipe
Reported or suspected cause
oil
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Leading evidence: 'oil' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'oil' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check air oil separator' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I have installed a �new� engine in my 996 c2 2002.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
25 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T122219Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I have installed a �new� engine in my 996 c2 2002. When I started it up everything worked fine. But after 5-10 minutes of idle a lot of smoke started to come out of the left exhaust pipe (but nothing from the right one). The engine sounded just fine. I am sure the smoke was caused by oil.
What could be the reason for the smoke?
Robert
The engine is used but new to me. I was a bit unclear before. I actually reved it a bit since I was adding coolant and I started and stopped it a few times. I should have said I ran it stationary.
I was thinking maybe I added a bit too much oil, but then why only smoke from the left exhaust pipe.
Robert
How many miles are on this motor?
What's the oil level on your dipstick? You can pull the AOS line from the throttle body and see if there's oil in it.
Did anyone scope the cylinders for scoring?
The engine has been used for racing. Totally rebuilt and then about 20 hours of racing. Shouldn�t bore scoring create bad noise from the engine? I looked into the cylinders with a camera but it looked fine from what I could see.
Yes, I replaced the engine myself. Nothing internal in the old engine was reused. My old engine got a seized rod bearing during a track day last year and became scrap.
Robert
Bore scoring doesn't start out with a noise. Did you scope the "new" engine cylinders from the oil sump or the spark plug holes? Jake points out in this video that bore scoring starts toward the bottom of the piston and may not initially be visible from the spark plug side of the cylinder.
You Tube
I just re-read your original post. you said "a lot of smoke". Are you sure it's not coolant? If the "new" engine is a 3.4 5-chain, they are more prone to cylinder head cracking which could lead to coolant in the combustion chamber. Post a video here if you can--someone on this forum (not me) should be able to distinguish oil smoke from coolant smoke/steam.
I'm dealing with a Nissan with a second blown head gasket that was supposedly "fixed" by Nissan under warranty, and a trick I learned from the tech there: Bring the engine up to operating temp, shut it down and immediately pull the spark plugs and then watch for leaks into the cylinder. Removing the spark plug eliminates back pressure and exacerbates the leak.
I'm surprised no one mentioned it. The "breather" hose for the AOS goes to Bank 2, the right side of the engine. Thus oil blow-by from the AOS ends up coming from the left exhaust pipe. If your lucky, maybe just a bad AOS. Pull throttle body and check the plenum for excessive oil, otherwise, and hopefully, just a faulty AOS.
That!
And OP stated that he started and stopped multiple times. My experience sometime those short start and stop, I get a puff of burned oil smoke out of exhaust. My understanding is that is AOS.
OP: Is oil filled to the top? What's a lot of smoke? Is it a big puff or continuous smoking?
I just talked to my mechanic. He is an independent Porsche specialist and rebuilds Porsche engines frequently. He believes that the smoke comes from oil from my old broken engine in the muffler. Since there are no fault codes it shouldn�t be anything serious according to him. Bad AOS would generate smoke from both exhausts and bore scoring should create sound if it was that much. He said that normally, bore scoring initially only results in oil consumption and not that much smoke.
So his advice was to just drive it some miles until the oil in the muffler is burnt away.
Robert
He is right about my bore scoring...no smoke. Don't remember if anyone asked...any unusual noises. Just to confirm previous engine hand grenaded? If so did the same side hand grenade which could have filled the exhaust?
Yes, my old engine said boom at the track. It was one of the right hand side rod bearings that seized (cylinder 6) and destroyed the engine so it makes sense that there are old oil residues in the left muffler.
Robert
Yep, if the old engine lost a cylinder on bank 2, the new engine is just cooking the oil from that muffler.. The muffler absorbs a lot of oil, and will smoke for a couple months after engine replacement normally.. I warn my purchasers about this, otherwise they are worried, anything worries people, and that drives me crazy.. You can now expect a primary O2 sensor code for bank 2 pretty soon, since the oil that fouled the muffler, also fouled the O2 sensor. These usually show up in a few hundred miles after a failure that dumps oil into the exhaust :-)
I clean them in the ultrasonic.. Ultimately heat has to do the job.
The catalytic converter is really where the oil is concentrated, and the source of the smoke is normally from the cat.
This is a source reference. Confirm exact model applicability in the original material.
