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Old 05-19-2010, 10:48 AM   #1
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Isn't the common test for a bad MAF to disconnect it...If the car runs better it's a bad MAF?
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Old 05-19-2010, 10:51 AM   #2
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with the money ya saved you can have the brakes fixed
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Old 05-19-2010, 11:37 AM   #3
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It's a good sign that the car is running now. It sounds you just have some bugs to work out. They are probably all or some of the following: bad MAF, dirty plugs, bad 02 sensors. The car is definitely going to start throwing codes soon which will help.

MAF:

Quote:
Originally Posted by Keith Newby
Isn't the common test for a bad MAF to disconnect it...If the car runs better it's a bad MAF?
In this case he's probably already in the limp home mode. So disconnecting the MAF may have no effect. It may be the MAF and disconnecting it is a very easy check. If the car runs the same or better with it disconnected then it might be the MAF. The maf is a wire that is heated and measures air flow by how much cooling it receives. In english that means there's a little silver wire that gets dirty. If you pull the MAF out using a security Torx wrench and look at it edge on you'll see where the air flows through it. There should be a shiny wire that air flows across. More likely you'll find a wire that's covered at least partially in what looks like gray fuzz. You can clean the gray fuzz off with acetone (nail polish remover), isopropynol (rubbing alcohol) or electrical component cleaner from autozone. It should be nice and shiny again with no residue when you're done. See if that helps at performance.

O2 sensor

My brother had a Ford with an early computer controller. He had very similar symptoms as you. His O2 sensor rusted out of the exhaust and was dangling under the car. The computer thought the engine was running very lean because it was just seeing fresh air. I haven't touched the boxster ones yet, but most people sem to replace all of them at once. Now might be a good time to go back and look at those codes that you had initially and use them to narrow down your search.
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Old 05-22-2010, 04:29 PM   #4
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Ok, so I cleaned the MAF and replaced the Spark Plug tubes as an excuse to pull a plug, and because, well, it was needed. See pics:

http://picasaweb.google.com/jondirty/Porsche#5474238721316082178
http://picasaweb.google.com/jondirty/Porsche#5474238737675537986
http://picasaweb.google.com/jondirty/Porsche#5474238755226869490

When the MAF was pulled, a cloud of dust erupted, so cleaning it appeared to be a good idea. The spark plug pulling indicated nothing unusual, and the tubes' O rings were definitely in need of replacement, but alas.. the car still isn't running well. It has no power above 3k right now, but it still hasn't thrown a new code yet since I cleared the codes below.. any more thoughts on what to try?

Jon
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Old 05-22-2010, 05:42 PM   #5
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Check to make sure that the butterfly valve in the intake rear is opening?
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Old 05-24-2010, 07:51 AM   #6
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Quote:
Originally Posted by cheetah
Check to make sure that the butterfly valve in the intake rear is opening?
in the throttle body?

Booked 2 O2 sensors to NAPA with wiring included, pre-cats, on the recommendation from my neighborhood Audi/Porsche mechanic. I'm going to replace those tomorrow and see if I can't get 'er running respectably..

J
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1999 Porsche Boxster 5 Spd
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Previous Toys:
2005 RX-8, RIP
1989 GTA, 5 Speed, Procharger Supercharger and 2 Core Intercooler, 1 3/4" headers, 3" Flomaster Exhaust, cat-delete, digital ignition, bigger fuel injectors

Last edited by Oaktown 986; 05-24-2010 at 12:53 PM. Reason: added O2 sensor purchase
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Old 05-27-2010, 05:50 PM   #7
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Quote:
Originally Posted by Oaktown 986
in the throttle body?


J

The rear cross-over pipe on the plenum has a butterfly valve that opens / closes with RPM, and I have heard that if that is not operating, as around 3K it really loses power.

That and fuel pressure would be easy things to check.
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