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Could be a number of things

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My 2002 2.7 base with 207K still my daily driver. Starting to have an issue with low speed lunging/surging going up a grade a low rpms (tiptronic). I am wondering if this is a transmission problem, and have been waiting for it to get worse before I take it to my local indy. If I downshift to increase rpm's, seems to go away. Any thoughts on what this could be?

BarryL
2002 2.7 Seal Grey Tip
Santa Cruz, CA
Does it also surge at idle speeds? If so, its probably an air leak.
Do you have any codes (including pending codes, which don't trigger the CEL)?

Tiptronic
MAF
Fuel delivery (clogged injectors, e.g.)

As I recommended in another thread, I would recommend running a bottle of Techron fuel system cleaner (not fuel injector cleaner) through the system and see if the problem gets better or goes away.
But before you go much further my recommendation is to have an experienced Porsche tech road test the car and advise you. He should be able to distinquish between a stumble/hesitation caused by the engine vs. one caused by a misbehaving Tip.

Assuming it is engine related, any pending error codes?
Hi Marc,

It's been a while since last service (9 months), about 40 k on spark plugs. Probably time to have my local Indy check it out. Thanks so much and I will post the out come. So great to have you still around on this board for invaluable source. Boxsterra too,

Barry
AOS failure on Sunday
BarryL - Yesterday at 10:41:53 pm
Coming back from golf up along the coast from Monterey. smoke began bellowing out my exhaust and I pulled over as soon as I could(about 30 sec). Engine lost power in vapor lock as I was coming to a stop. Flatbed tow to my local Indy. He will be working on it tomorrow but indicated total engine freeze up. He seemed confident he could drain oil out of the spark plugs holes and that it should be fine. Fingers crossed.

BarryL
Re: AOS failure on Sunday
MarcW - Today at 7:59:54 am (9 hours ago)
My 2002 Boxster suffered something similar although at the hands of the tech when I had it in for what proved to be the first AOS replacement of 3 (so far).

The lock up occurred while the car was in for the AOS replacement. Not sure of the circumstances now. (I recall being told the lock up occurred during a compression test. A compression test was apparently "SOP" in these cases which is insane in my opinion.)

Apparently the lock up didn't do any harm. That was at around 80K miles and the engine has over 313K mile in total on it now and still runs fine. And it has suffered 2 more AOS failures both which ended in the engine smoking like crazy but in which the engine was shut off and not run anymore until after the AOS was replaced.

When you get your car back the engine will probably smoke upon the 1st and maybe the new few subsequent starts especially if the engine is not run much after the AOS was replaced or you don't run the engine much when you drive it. It takes time for the oil that has gotten into the intake due to the failed AOS to work its way out of the engine.

You want to try to run the engine a while to get the engine fully up to temperature and ideally the intake warm as it can be which means driving the car around town with its stop and go driving which has the intake as warm as it can be.

The engine may trip a check engine light so don't be too surprised if this occurrs. The odds are the light arises from the oiling the engine was subjected to and the oil in which is being worked out of the engine. So a read of the code or codes, a check for any pending codes, and after writing all these down just clearing the codes followed by a road test to see if the CEL comes back on is called for.

If you want a treatment of Techron could be called for. Get a bottle that treats 20 gallons and at the gas station shake the bottle then dump its contents in the gas tank followed by filling the gas tank with whatever premium gasoline you use then just driving the car. The Techron will remove any engine deposits -- those that have been accumulated from the recent "oiling" and any that were present before. The general rule is if you notice any improvement in how the engine runs to follow the 1st bottle with a 2nd bottle after the gas with the first bottle added is way down to say a quarter a tank. My advice would be to just plan on using two bottles -- one right after the other -- regardless.

After the last tank with Techron is down to 1/4 of a tank or so then plan on having the oil and filter replaced. The Techron in doing its job can add to the oil's contamination level and it is best to then remove this oil and the filter.
This will be my 4th AOS. Like in your case, my mechanic didn't expect there to be a problem in getting this cleared and back on the road. He said there is a lot of inaccurate hype on the internet that this type of event destroys engines. It came on so fast, without warning and I shut it down pretty soon, but not immediately as I was in on highway 1 coming up the coast and it took me 30 sec to find an place to safely pull over. Funny I was thinking it was about time to replace the AOS, but didn't act preemptively. He will be working on the car today.

BarryL
Quote
BarryL
This will be my 4th AOS. Like in your case, my mechanic didn't expect there to be a problem in getting this cleared and back on the road. He said there is a lot of inaccurate hype on the internet that this type of event destroys engines. It came on so fast, without warning and I shut it down pretty soon, but not immediately as I was in on highway 1 coming up the coast and it took me 30 sec to find an place to safely pull over. Funny I was thinking it was about time to replace the AOS, but didn't act preemptively. He will be working on the car today.

BarryL

4?! Thought being on the 3rd replacement AOS (4 total) I was the record holder, but I guess not.

While it is not common for an engine to be destroyed there is the risk. I always caution owners that if an AOS is suspected don't delay in getting it diagnosed and if found to be bad replaced.
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