Ahsai

I think this is worth trying even though it's not too intuitive. Good luck and keep us posted. Mmm, ok. I will try this. This seems opposite of what all other drive cycle guideline's instruction - which is to let the car idle 2-5mins. Has anyone seen the status would flip right away after the pump shuts down or do I have to perform the full drive cycle?

Yeah, try unplug the MAF and reset the DME also and see how the car drives.

Glad to see you fixed the 1128/1130 codes and thanks for the update.

BTW, one possibility is a sticky evap purge valve (that feeds into the throttle body). It can create a too lean or too rich condition, depending on how rich or lean the fuel vapor is at the time in the gas tank.

I checked your log. The problem is intermittent. When it occurs, the MAF read very high even at idle speed. It was 7g/s (i.e., 25.2kg/hr) or higher. The fuel trim pegs out at -25% (short term fuel trim) so the engine was running rich. All O2 sensors have high sustained (0.7v) voltage (too rich). Is the MAF a Bosch unit? Also, when this condition happened, the throttle position always read 2.35239% fixed. That looks odd. Also, LTFT values are always fixed so not sure how much we can trust the Torque log values.

Is it possible some clutch hydraulc lines were pinched when you jacked up the car? How is the brake fluid level?

Can you also try e-gas recalibration to see if it helps?

Are you sure the plenum connections are air-tight. Those hose clams can be tricky. Perhaps retrace what you have removed and reinstalled and make sure all the connections (electrical connectors as well) are tight?

A light coat of oil is normal. It's hard to tell from the photos. They don't look too bad to me though.

That looks good me. I'm not sure if the slight vacuum fluctuation when you blipped the throttle is normal or not. Probably it is.

Removing the distribution tube is easy (figure 7 here http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/09-ENGINE-Air_Oil_Separator/09-ENGINE-Air_Oil_Separator.htm ) I'm not sure if you can get away with removing the alternator only or plenum only though. The black/white valve should just plug into the left rubber intake plenum sleeve. Pics of the whole system here http://rennlist.com/forums/996-forum/849770-mkii-996-vacuum-line-routing-and-related-components.html May as well replace the vacuum reservoir and all the hard tubing.

The P0102 means MAF no/low signal, shorted to ground, etc. I would check the MAF electrical connection and continuity of the wires between the MAF and the DME.

What MAF and p/n are you using?

SOP for addressing rough idle is cleaning the throttle body and the idle stabilizer thoroughly first.

Not too close to you but I think it will be worth the drive Tony Callas http://www.callasrennsport.com/

And some epoxy or sealant to seal it too.

Be careful with the plastic ones though as brake fluid can destroy some plastic from inside out. Not sure why but that's my experience. The metal one I got is unbreakable :)

I use a syringe like this with a white plastic straw from a juice box attached. It works really well and won't drip like the turkey basters. http://www.amazon.com/Physician-Supplies-Ear-Syringe-Metal/dp/B0008G1ZRS/ref=sr_1_3?ie=UTF8&qid=1456163856&sr=8-3&keywords=ear+cleaning+syringe

Great. Yes, I just modified my old cap, bought and installed a new one on my engine.

That and to verify the new AOS is working properly. If you don't measure, you may also change out a good AOS unnecessarily. These meters are getting cheaper. http://www.amazon.com/gp/aw/d/B00N3PPZZY/ref=mp_s_a_1_2?qid=1456019143&sr=8-2π=AC_SX236_SY340_FMwebp_QL65&keywords=digital+manometer

Agree with John if you switch out the AOS before measuring the crankcase vacuum, you lose a valuable and critical data point/clue. Also keep in mind a new AOS can fail out of the box so a manaometer measurement is needed anyway to verify the new AOS is indeed working. Blindly swap out components may introduce more variables and lead you chasing your tail. More than the data this could yield, I'd still like to know what the crankcase vacuum level is on your car; one min. of diagnostic time would immediately confirm or deny the AOS is going bad. I'd be willing to bet that we would see a vacuum signal somewhere between 5 and 10 inches of water; enough to be annoying and causing running issues, but not yet shot enough to disable the car and turn it into a mosquito fogger. Oh the joys of long distance diagnostics...........

John, this is interesting. Why will AOS leak make MAF read higher? Even I have a setup like that at home :) You have hit on the $64 dollar question. We know from direct experience that MAF's on their way to "aging out" often read higher than expected air volume flows; we have seen this on Porsche's as well as other brands, so it is not an unexpected event. So when we saw higher than normal MAF air volume numbers on cars with obviously dying AOS units, we kind of wrote it off to an aging sensor. But then someone brought it to my attention that they had seen similar high air flow volumes on cars with bad AOS units, that subsequently (but not always) dropped back into range when the AOS was replaced, so it was not always a dying sensor. Always intrigued by a new mystery on these cars, and not wanting to needlessly be replacing expensive MAF units, we started looking at cars we got in that failed the AOS vacuum test (vacuum signal at the oil fill caps greater than 5 inches of water). And what we saw mimicked what the other observer noted, the air flow volume often changed, which set us scratching out heads. On the 986 in question for example, the AOS line to the intake system enters behind the throttle body and ahead of the intake plenum, and the MAF is located a couple of feet "upstream" of the throttle body, near the air filter box on the driver's side rear fender; so intuitively it would seem rather too remote to see a change in the vacuum signal level where the AOS line enters the intake. But it apparently does under some conditions. Why this happens remains an item of speculation, and the amount of air volume change is not always large, but always seems to be in the same direction when it happens. An interesting experiment would be to set up a car to mimic a failing AOS (which would require being able to "throttle" the AOS crankcase vacuum level up or down, while monitoring both the intake plenum vacuum levels and the MAF air flow volumes) and collect some additional data points in an attempt to see what is going on. Unfortunately, in the shop we are nearly always in a time crunch to figure out what is wrong and get the car back into the owner's hands, so we have not attempted this. It would be an interesting R&D experiment however. Thanks John for the detailed reply. My thinking is as follows: Suppose everything is working correctly on a warmed up idling engine. Now all in a sudden the AOS diaphragm cracks. That allows MORE crankcase gas (oxygen deprived and even fuel-enriched) into the throttle and LESS fresh air from intake, Both effect will create an instantaneous rich condition. Engine will start to stumble due to wrong a/f mixture. To maintain a minimum rpm, the DME compensates by opening up the throttle a bit more to let more fresh air (oxygen) into the engine to achieve the correct a/f ratio. At the end the MAF will see more flow (in mass per second) and the rpm may be raised a little too (not sure about this though). When you observed the MAF read a bit higher than normal, I assume the rpm was at a normal value and not raised? I mean if the rpm was also raised, it's just natural the MAF read higher. I think it will be quite difficult to simulate the crack inside the AOS precisely. One will need to build an adjustable bypass valve between the AOS vent tube that's connected to the crankcase and the AOS vent tube that's connected to the throttle body. Will be an interesting experiment nonetheless :) I would expect that if the your scenario were correct, the idle should go up and down, and with the repeated A/F issues, the car would also code because the mixture would eventually have to swing out of range one way or the other more than once. We observed the higher MAF volume numbers at a normal (and steady) idle speeds. The basic problem with the AOS design is that it is way too complicated, too fragile, and has too many ways of going south on you. We thought about how you would have to modify one to test our observations and it quickly turned into a plumbing and electrical nightmare. Sometimes the view just ain't worth the climb............. Actually I expect it to stabilize and not oscillate because once the throttle plate cracks a little bit more, more O2 will be sucked in to neutralize the rich condition. If my thinking is right, we should observe the throttle plate angle is larger than normal. To have the (working) MAF read higher, either the vacuum suction from the engine increases or the throttle plate opens more. I expect the leaked crankcase gas will decrease the vacuum so if the rpm remains the same, I would expect the throttle plate opens more than notmal.

John, this is interesting. Why will AOS leak make MAF read higher? Even I have a setup like that at home :) You have hit on the $64 dollar question. We know from direct experience that MAF's on their way to "aging out" often read higher than expected air volume flows; we have seen this on Porsche's as well as other brands, so it is not an unexpected event. So when we saw higher than normal MAF air volume numbers on cars with obviously dying AOS units, we kind of wrote it off to an aging sensor. But then someone brought it to my attention that they had seen similar high air flow volumes on cars with bad AOS units, that subsequently (but not always) dropped back into range when the AOS was replaced, so it was not always a dying sensor. Always intrigued by a new mystery on these cars, and not wanting to needlessly be replacing expensive MAF units, we started looking at cars we got in that failed the AOS vacuum test (vacuum signal at the oil fill caps greater than 5 inches of water). And what we saw mimicked what the other observer noted, the air flow volume often changed, which set us scratching out heads. On the 986 in question for example, the AOS line to the intake system enters behind the throttle body and ahead of the intake plenum, and the MAF is located a couple of feet "upstream" of the throttle body, near the air filter box on the driver's side rear fender; so intuitively it would seem rather too remote to see a change in the vacuum signal level where the AOS line enters the intake. But it apparently does under some conditions. Why this happens remains an item of speculation, and the amount of air volume change is not always large, but always seems to be in the same direction when it happens. An interesting experiment would be to set up a car to mimic a failing AOS (which would require being able to "throttle" the AOS crankcase vacuum level up or down, while monitoring both the intake plenum vacuum levels and the MAF air flow volumes) and collect some additional data points in an attempt to see what is going on. Unfortunately, in the shop we are nearly always in a time crunch to figure out what is wrong and get the car back into the owner's hands, so we have not attempted this. It would be an interesting R&D experiment however. Thanks John for the detailed reply. My thinking is as follows: Suppose everything is working correctly on a warmed up idling engine. Now all in a sudden the AOS diaphragm cracks. That allows MORE crankcase gas (oxygen deprived and even fuel-enriched) into the throttle and LESS fresh air from intake, Both effect will create an instantaneous rich condition. Engine will start to stumble due to wrong a/f mixture. To maintain a minimum rpm, the DME compensates by opening up the throttle a bit more to let more fresh air (oxygen) into the engine to achieve the correct a/f ratio. At the end the MAF will see more flow (in mass per second) and the rpm may be raised a little too (not sure about this though). When you observed the MAF read a bit higher than normal, I assume the rpm was at a normal value and not raised? I mean if the rpm was also raised, it's just natural the MAF read higher. I think it will be quite difficult to simulate the crack inside the AOS precisely. One will need to build an adjustable bypass valve between the AOS vent tube that's connected to the crankcase and the AOS vent tube that's connected to the throttle body. Will be an interesting experiment nonetheless :)

John, this is interesting. Why will AOS leak make MAF read higher? Even I have a setup like that at home :)

I am ('03 996 70k miles).