19 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHAir/Oil Separator
Reported repair
Replace oxygen sensors
Reported resolution
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Discussions that report a fix
1
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Reported fix
I finally diagnosed the problem to a bad O2 sensor and replaced it, had dealer replace just the one I diagnosed. Problem solved.
Leading evidence: 'Replace oxygen sensors' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is '2nd maf' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace oxygen sensors' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Replace oxygen sensors', supported by resolution reports in 1 discussions. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that report identifying a cause
1
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Reported cause
The original one worked just fine and it was the 2nd MAF, that had racked up close to 80,000 miles.
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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
I even cleaned the MAF the first time -- after 80,000 miles from new -- and found no dirt on the MAF.
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.
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Performed · outcome unconfirmed
water filled monometer, that's the words I was looking for.
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.
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Performed · outcome unconfirmed
Interestingly enough, the only way to test the oil separator is to periodically test the engine crankcase vacuum with a water filled Monometer AKA an ultrasensitive vacuum gauge.
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Suggestion
The only way to know what is/was happening is to check the fuel trim numbers on the OBD-II “Freeze Frame” data and crankcase vacuum to see exactly what’s going on, otherwise your just guessing.
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Performed · outcome unconfirmed
Interestingly enough, the only way to test the oil separator is to periodically test the engine crankcase vacuum with a water filled Monometer AKA an ultrasensitive vacuum gauge.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
A normal/healthy engine and engine controller can very easily adapt to the removal of the oil tube filler cap and of course its being installed afterwards.
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.
19 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.
2 acknowledgements have no verified action link; they do not establish a repair result.
This may be one of those "don't trouble troubles unles trouble troubles you" topics BUT:
I was driving my car a few months ago and it was idleing poorly. I had added some oil and left the oil cap loose. Once I put it on properly, no problem. While searching a thread here, I saw a check for a/o separator that said "take the oil cap off, if the cars stalls the a/o separator is bad". So I took my cap off and again the car ran rough but didn't stall. I put my hand over the oil fill and felt a slight negative pressure.
Mind you, I have no other symptoms that I know of (ie no smoke, no check engine light...nothing).
Should I be concerned? Any other checks?
Pat, if it doesnt kill the motor, you are more than likely ok.
When mine went, it made a metal to metal screeching sound, similar to a bad idler pulley that squeeks every revolution of the motor.
Once the oil cap was removed, it instantly leaned out and died.
When I put the new one in, it barely affected idle and just had a minimal drop in RPM. The vacuum pull was very low but evident.
Hope this helps.
Welcome. I forgot to add, it only dropped RPM once the oil cap was removed with the new AOS and the squeeking sound that sounded like a bad idler pulley but was very, very loud. It was embarassing.
However, that is not always the case...
When mine went, idle increased and cold starting was more problematic. There is a test for the AOS. Callas Rennsport had some sort of tube thingy gauge. It took a few seconds and they could see the AOS was bad.
If the intake system and AOS is functioning properly, Porsche specs call for the idle to slightly increase (+40 rpm) and timing to be pulled a little (1.5 degrees) when the oil cap is removed.
Although, not sure if it is a result of AOS failure, a Service Manager said that when the AOS fails, it takes out the MAF with it. I thought BS when I was leaving with the new one.
But, when I was trying to rid my car of the CEL (new AOS installed), we searched an o2 problem (what we thought from the print-out) for a few days on mine and sure enough, the MAF was dead as he said.
I still can't figure this one out and still feel it is coincidental.
cap did not kill engine, cause I couldn't remove it against the pressure difference! Unscrew it, yes. But could not lift cap off.
I could see if AOS pulling that much vacuum that if one could get the cap off it could overwhelm the engine controller's controller's ability to adapt and the engine could die.
A normal/healthy engine and engine controller can very easily adapt to the removal of the oil tube filler cap and of course its being installed afterwards.
Second time AOS failed there was alot of oil smoke upon startup that continued. Always before when there was oil smoke upon startup and this rare it was just a brief event. But in this case the engine just kept emitting a steady cloud of oil smoke.
In both cases MAF was unaffected. I even cleaned the MAF the first time -- after 80,000 miles from new -- and found no dirt on the MAF. Used cleaner and let cleaner fluid drip on clean white paper towels and no dirt. The throttle body now was dirty, a bit oily.
Second time I never even bothered to clean the MAF or have plugs replaced. Just had car flatbedded to dealer and had the AOS changed.
In both cases afterwards, I ran a bottle or two of Techron through engine -- following directions -- to help remove any engine deposits the oil burning might have caused. I changed the oil afterwards, too, which is my standard operating procedure after using Techron.
Sincerely,
Macster.
bad.
Several years ago car emitted error codes that hinted at a MAF problem. Even got a sort of diagnosis from dealer tech who when I had car in for something else hooked up computer and told me the MAF adaptation was wrong.
Finally broke down and bought a new MAF to replace the original MAF that had been in the car since new (since '02 and had racked up oh roughly 120,000 miles at that time).
New MAF appeared to solve problem for a day or so. Then the error codes came back. Looking over car some more with co-worker and he heard (my hearing's not good) a vacuum leak around oil tube filler cap. Replaced this for less than $20 with new one. Problem solved.
This new MAF recently became suspect and after ensuring the oil tube filler cap not leaking I replaced this second MAF with the original one I had saved.
The original one worked just fine and it was the 2nd MAF, that had racked up close to 80,000 miles. (Car now has over 207,000 miles on it.)
The only way a failing AOS could take out a MAF is if tech drops wrench on MAF while removing AOS. Now it could be that MAF was just ready to go bad and it going bad was just a coincidence. These do happen.
Oh, after 1st AOS, car still emitting error codes. I forget now what they were. I finally diagnosed the problem to a bad O2 sensor and replaced it, had dealer replace just the one I diagnosed. Problem solved. In this case the failing AOS and the dose of oil it fed the engine may *may* have accelerated the demise of the O2 sensor, though I note that at 80,000 miles the O2 sensor could have been probably was near the end of its life anyway.
Sincerely,
Macster.
HAHA, mine sounded like a whale getting had.......or a Hayena (sp?)
The sound I believe is just the rush of air either past the ruptured diaphram or simply through the housing itself.
No, I meant when I would remove the oil cap after I put in the new AOS, it only raised the RPM by about 50 as '99 said.
Yepper, mine was almost impossible to remove the first time. Yeah, the engine is injesting large amounts of crankcase air through the bad AOS up to the intake plenum past the metered air.
Yeah, I think it is coincidence as I stated before. But, luckily, the new owner has not had a CEL since. (cross fingers) I offered lifetime repair if he ever had problems.
The Engine oil air separator directly affects the engine crankcase atmosphere because basically all Porsches from 1980 on including the current 986-987-996-997-Caymen & Cayenne engines are all positive crankcase type systems meaning the engine crankcase has vacuum supplied from the intake manifold to collect and burn the residual combustion by-products or blow-by in the crankcase by running it through the engine again, basically to lower the overall vehicle emissions.
On most occasions, when the oil separator fails, intake vacuum in the engine crankcase rises to an unusually or abnormal rate and more likely than not ends up drawing engine oil into the intake system usually fouling spark plugs and even possibly causing damage to the oxygen sensors (O2), catalytic convertors and even possibly various other sensitive fuel injection components.
Interestingly enough, the only way to test the oil separator is to periodically test the engine crankcase vacuum with a water filled Monometer AKA an ultrasensitive vacuum gauge. On BMW’s and Porsche’s, the engine crankcase vacuum is normally around 4-7” (Inches) of water. When these oil separators fail the crankcase vacuum can rise to 9-12” and even higher depending on the extent of the failure.
When the oil separator is starting to fail on Boxsters (986-987), generally you will start to see a substantial amount of smoke from the exhaust tailpipe. When the oil separator finally fails, the engine exhaust smoke can reach dangerous proportions that almost look like it was manufactured from an anti-mosquito smoke machine. Unusually enough, on the 999-997’s, when the oil separator fails, it hardly ever creates any exhaust tailpipe smoke, almost being like a silent killer or costly surprise.
On another note, it has been known on rare occasions, that when an oil separator fails that it is possible to cause or create a slightly rich running condition that might turn on the check engine light or CEL.
The only way to know what is/was happening is to check the fuel trim numbers on the OBD-II “Freeze Frame” data and crankcase vacuum to see exactly what’s going on, otherwise your just guessing.
Hope this helps,
Tony
No problem Chris, thanks for the support. I am always scanning the boards and forums to see if technical help is needed because in the end we all benefit from it. I started teaching an advanced class for Porsche technicians combining forces with a company known as World Pac Training Institute, so now I enjoy the educational aspect of this from another angle. Some of you guys are very mechanically savvy so here is a link just incase anyone is interested.
http://www.worldpac.com/wti.html
