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YOUR RESEARCHMy turn for some engine trouble...
Reported or suspected cause
aos failure i found there was oil
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
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Read evidence and context
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Reported cause
Also, what I found in dealing with what proved to be an AOS failure I found there was oil on the throttle body and its butterfly valve.
Leading evidence: 'aos failure i found there was oil' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'aos failure i found there was oil' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace aos, regardless' (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.
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Reported cause · Original poster
It was the color of the oil but had the consistancy of water.
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Reported cause · Original poster
It was the smoke from one side that made me very uneasy.
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Suspected cause
(This sort of behaviour was sufficient to make me suspect the MAF which I replaced only to find a few days later -- after the error codes returned -- it was a $13 cap and not a $300+ MAF.)
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Suggestion
Well, the car has 98,000 miles on it, so if I were you, I'd replace the AOS, regardless.
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Unsuccessful attempt
(This sort of behaviour was sufficient to make me suspect the MAF which I replaced only to find a few days later -- after the error codes returned -- it was a $13 cap and not a $300+ MAF.)
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Suspected cause
(This sort of behaviour was sufficient to make me suspect the MAF which I replaced only to find a few days later -- after the error codes returned -- it was a $13 cap and not a $300+ MAF.)
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Let me start by saying that I purchased my 996 C4 in November and have driven it about 4k miles since then... it now has 98k on the clock. It doesn't leak and I've had no issues with it up until now.
I recently went away for 10 days and left the keys to the person that was watching the house while I was away. I knew it would probably be driven.. and possibly hard... while I was gone. The person has driven it before and owns an 04 Turbo so I wasn't too worried.
So, fast forward to today... start the car up and it was a little louder then normal and felt slightly rough. I didn't think anything of it. Drove about a mile and the CEL came on and the car began to lose power and run really rough.
I pulled into a parking lot and let the car idle. The CEL went off and the car idled just fine. Go to drive it again and the CEL began flashing and it was rough. As I drove back home, the CEL only flashed if I took it above 3-4k RPM so I stayed below it.
Turned it off in my garage and let it sit a minute. When I turned it back on, I got a bunch of (what I believe was white-ish gray) smoke out of the passenger side tail pipe. CEL was solid but the car was running.
I didn't see any evidence of oil in the coolant overflow, oil looked ok on the dipstick, and nothing was leaking out of the car.
So lets see... head gasket? cracked cylinder head? AOS?
I'm going to have it towed to a local shop on Sat but was wondering if anyone had some ideas... am I talking $$$ .... or $$$$... or hopefully not $$$$$!!!
Thanks,
-JRW
Sounds like a variocam actuator producing misfires, but it's just a guessing game without the codes.
Certainly have the car towed if the CEL ever flashes (or read the codes and resolve the problem).
It may be painful, but I would start by having a serious heart to heart with your house sitter. Something like: "I promise not to hit you if you tell me exactly what happened while you were driving my Carrera". Worst case it sounds like you are leaking oil or coolant into a combustion chamber. Ouch!
+1 for varicam stuck. If not that then bad coil packs and/or AOS. Did your "friend" maybe leave the car out in the rain? If so then I would say coil packs.
Get the code(s) read and report back.
Thanks for all the responses guys. I know the codes are important ... I should have just bought a code reader to start with.
I guess I just wanted to see what everyone thought since I was in a bit of a panic this morning when this all happened... I'll be sure to report back with some more information... and probably some more questions.
Thanks,
-JRW
The smoke points to a problem with the AOS, which is not a big deal. To check it, start the car, if you dare, take off the oil filler cap and put your hand over the filler tube to seal it off. You should feel a barely perceptible vacuum. If you feel any significant vacuum, the AOS is probably bad.
Maybe a dumb question from an air cooled owner here, but does could the AOS also cause the rough running the OP is describing? Curious b/c looking at maybe moving to a 996.
A bad AOS is hard to diagnose. Normally a bad AOS will smoke and not stop smoking.
Also starting the car and turning it off immediately and restarting the cars will cause a plume of smoke.
If there is mis-firing and oil get passed the valves you also gona see smoke.
Smoke coming out only one side is more of an attention getter to me and probably could be more of a major problem.
Depending upon the severity of the AOS failure it can cause rough running. The AOS failing represents a big air intake leak which while the DME will try to adapt will have a tough time of it.
At some point the DME will lkely reach its enrichment threshold and set the CEL.
A problem is that in some cases as engine rpms rise the AOS air leak represents a smaller precentage of air being allowed into the engine so the DME will then try to unwind what it did when the AOS represented a larger percentage of air being allowed into the engine.
(This sort of behaviour was sufficient to make me suspect the MAF which I replaced only to find a few days later -- after the error codes returned -- it was a $13 cap and not a $300+ MAF.)
Also, what I found in dealing with what proved to be an AOS failure I found there was oil on the throttle body and its butterfly valve. I cleaned this assembly thoroughly and a mildly rough running engine smoothed out but soon developed its rough running ways.
In addition to the air leak in some cases this failure routes considerable oil vapor (and in the later stages of a severe AOS failure possibly even liquid oil) to the engine. This upsets combustion and rough running along with prodigious amounts of oil smoke from the exhaust outlet results.
Sincerely,
Macster.
Smoke coming from just one cylinder bank can be the AOS. The AOS has a hose that connects to the intake manifold just after the TB. At least this is the case with my Boxster and I assume the 996 has some similar arrangement.
If the AOS goes bad enough that it is routing oil vapor and even oil the engine this hose connection favors one cylinder bank over the other so one bank will smoke while the other may not smoke.
Sincerely,
Macster.
That does make me feel better. It was the smoke from one side that made me very uneasy. I know it could still be a head gasket or even worse a cracked head... we will see.
I didn't get any service records but talked to the mechanic of the previous owner who did state that in the six years that he had serviced the car they had done a water pump, AOS, and small things like brakes and oil changes.
So, I just went out and bought a code reader but won't be able to put it on the car until tomorrow. Ill get some codes and report back. If it seems like smaller items like the AOS or coils could be the fix, I might just do that myself.
Thanks for your help!
-JRW
Ok, its CODE TIME!
I purchased an Actron CP9580. It fired right up and gave me 6 codes.
P0159 - Aging of Oxygen Sensor After Catalytic Converter (Cylinders 4 - 6)
P1118 - Oxygen Sensor Heating After TWC, Bank 2 � Below Limit
P0300 - P0300 Misfire Damaging to Catalytic Converter
P0301 - Misfire, Cylinder 1, Damaging to Catalytic Converter
P0302 - Misfire, Cylinder 2, Damaging to Catalytic Converter
P0305 - Misfire, Cylinder 5, Damaging to Catalytic Converter
The car starts right up and runs with a decent idle... slightly rough but not even close to dying. After about a min there was a slight bit of smoke from the passenger side tail pipe so I shut it off.
** UPDATE **
So, I drove it out of the garage and over to another bay to get it up on a lift. I had the engine running for less then 2 mins. Again, just before I shut it down, large amounts of smoke were pouring out the passenger side tail pipe.
Up on the lift I could see a bit of oil around the AOS mostly on the bellows.
What worries me the most was a leak coming from the passenger side exhaust at the joint before the tail pipes. It was the color of the oil but had the consistancy of water. There wasn't a ton but it had sporadic drips for a few mins after the engine was off.
I pulled the dip stick and it seemed like it was only oil... kinda hard to tell. The coolant overflow seemed to be 100% coolant .... even tried stirring it up with a screw driver.
Sooooo.... I'm torn here. Could I be on my way by replacing the AOS, spark plugs and tubes, along with O2 sensors and possibly cats? Or, is this a a head gasket or a crack in the cylindar head?
I'm willing to do this first bit of stuff... but dropping the engine and doing head work is beyond what I want to do myself.
**
So, what do you recommend? I'm looking forward to your replies!
Thanks,
-JRW
Why not try swapping the o2 sensors and see if the problem pops up on the 1-3 bank instead?? I would think if it is the AOS your more likely to get smoke out the driver's side since the vent attaches on that side of the plenum.. I maybe wrong.
Well, the car has 98,000 miles on it, so if I were you, I'd replace the AOS, regardless. It may solve the problem, or it my not. However, it is about due, so you might as well take care of it now.
Probably gonna need a bit more info here ... does the leaked fluid smell like gas? It may very well be a dead AOS. Or a stuck or damaged exhaust valve (hopefully not). Either way the cats are probably dead. I think a failed MAF could cause these codes/symptoms as well.
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