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Old 12-08-2010, 02:07 AM   #1
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Need help diagnosing MAF related issues...

I'm not very mechanically minded so I will try to explain this to the best of my ability.

Early last year, due to the rough idling and throttle hesitation problems I cleaned the MAF following mikefocke's DIY, and it solved all the problems.

A few weeks ago, the throttle hesitation came back, I cleaned the MAF again and the problem went away for a week or so. Until last weekend, out of no where, the engine wouldn't rev pass 3k rpm and stalls intermittently. I unplug the MAF and all was fine again. So it seems to me the MAF has failed at last and I'm in the process of ordering a new MAF through ********************************.

I have also discovered some oil leaks on the part (not sure what its called?) directly below the throttle. See attached pics.





Another issue worth mentioning is, my mechanic found the engine running very lean on startups, by putting a "sensor" in the exhaust. But he doesn't have a Porsche "ecu reader" (sorry I don't know what the correct term is) to know the cause of it for sure.

Could these symptoms be related to an AOS failure? I tried removing the oil fill cap while the engine is running. It can be removed but I could hear the revs adjusting while the cap is being removed. So there is a bit of a vacuum. I don't know if it means anything?

I would appreciate any help.



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Old 12-08-2010, 03:36 AM   #2
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OK if I understand correctly you are going to install a new MAF, which sounds like a good plan. The top pic looks like the J tube for the AOS, the bottom pic is the lower connection for the AOS it might be time to look at it too if the car smokes more than the expected start up puffs.
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Old 12-08-2010, 06:01 AM   #3
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Quote:
Originally Posted by eightsandaces
OK if I understand correctly you are going to install a new MAF, which sounds like a good plan. The top pic looks like the J tube for the AOS, the bottom pic is the lower connection for the AOS it might be time to look at it too if the car smokes more than the expected start up puffs.
Yeah I will be replacing the MAF either way. Just thought if I should also look at the AOS since I can see a bit of oil down there but it's not dripping or anything...

The 2nd and 3rd are the same pic (one with flash). The top pic was shot from the same position but with a wider angle so the viewer can see where exactly the oil is, in relation to the throttle body.

So the oil is at the lower connection for the AOS? The car does not seem to have more than expected smoke during start ups. Although it always had more smoke than other cars I own.
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Old 12-08-2010, 06:11 AM   #4
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Quote:
Originally Posted by panameras
Yeah I will be replacing the MAF either way. Just thought if I should also look at the AOS since I can see a bit of oil down there but it's not dripping or anything...

The 2nd and 3rd are the same pic (one with flash). The top pic was shot from the same position but with a wider angle so the viewer can see where exactly the oil is, in relation to the throttle body.

So the oil is at the lower connection for the AOS? The car does not seem to have more than expected smoke during start ups. Although it always had more smoke than other cars I own.


It's a characteristic of H6 or flat 6 engines, completely normal, I'd leave the AOS alone then and just replace the maf, see if that doesn't cure what ails ya..
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Old 12-08-2010, 06:33 AM   #5
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Lets start by assuming that the two problems are connected

and that the AOS may be suspect.

Have the mechanic remove the air intake tube and look at the condition of the throttle body. If the tube and TB are oil covered, then the MAF signals may not be bad, just unable to do their job controlling air/fuel mix due to the oil on the throttle plate. (Good cleaning instructions on Pedro's site)

I'm assuming you run a stock air filter and not an oiled replacement unit.

You didn't say (or I don't remember) how many miles on the engine and specifically the AOS.

It isn't a bad move to periodically replace the AOS. You may get away with the AOS, and the cleaning and not have to replace the actual MAF. Or it may be all of the above.

Do you have access to a Porsche mechanic who has the proper diagnostic equipment? Sometimes paying a bit extra there will save the costs of shotgunning parts until you eventually hit on the one that is causing the problem. Plus a Porsche mechanic will know exactly what to look for to pinpoint if it is the AOS that is at the root of the problems.
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Old 12-08-2010, 11:44 PM   #6
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Thanks for the reply Mike

I am running a stock air filter. The car has just over 50k miles, I haven't replace the AOS since during my ownership (bought it at 35k miles) and I'm not sure if it has ever been replaced.

I will get my mechanic to check the intake and throttle body and have them cleaned while at it. Might as well replace the AOS if it's not too expensive? I can always keep the new MAF as a spare.
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Old 12-18-2010, 08:06 AM   #7
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An update,

My mechanic and I cleaned the throttle body, intake tube and the T pipe, there were only a little bit of oil in them, not enough to cause MAF malfunction, we didn't think. We also decided to replace the AOS anyway since its not too expensive. We then reconnected the existing MAF and the symptoms (rough idling, hesitation when revving, etc) were still there. But as soon as its disconnected, all is smooth again.

Good news my replacement MAF has arrived from ********************************AZ, thanks to their excellent customer service (US to AU in less than a week)!
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Old 12-18-2010, 08:11 AM   #8
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Dealer DME reflash necessary?

My new MAF has the part no. 996.606.125.01

The car is a 2000 E-gas model and the replaced MAF has part no. 996.606.124.00

Does it require a DME reflash? The car seems to be running fine with the new MAF installed although I haven't taken it for a longer drive yet.


p.s. it has a GIAC flash currently, if that makes any difference.


Last edited by panameras; 12-18-2010 at 08:14 AM.
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