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Old 02-04-2009, 10:01 PM   #1
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Check Engine Light

Hey guys,

First timer here. I'm not exactly sure where this is supposed to be posted but hopefully this should be good. I just bought my 2000 boxster s about a few months ago and I already got a check engine light (CEL). The guy I bought it from said this was normal since he hasn't replaced his O2 sensor for the one ahead of the catalytic converter for bank 1. He has this software where I hook it up to a laptop and it will allow me to reset the codes in the car. I saw that the 02 sensor was there but there was also a Idle Air Control System (IACS) error. It spits out a P0507 for it. I reset the codes and the CEL went away.

A few days later it was back on the dash. It was then that I decided to figure out what the error meant which I found to be either the throttle valve is sticking or an air intake leak. Yesterday, I removed the throttle valve with the sensor and cleaned off the inside. It didn't appear to be extremely dirty but there was some gunk so I got rid of it and put it back in the car. Upon doing this, the CEL was gone only to return again the next time I took it out.

I called up some dealerships and they were saying that the first thing they do is replace the throttle valve. It didn't seem to me like it was sticking and I cleaned it out pretty well so I'm not sure if thats my problem. Another dealership told me he thought it could be a mass air flow sensor or a bad air oil separator (AOS). He also explained how I could determine if my AOS is indeed working without having to get into the car engine.

He told me to remove the oil dipstick and to feel for suction. If there is a constant suction, then the AOS is bad. If there is suction and then air shooting out like in a cycle, then that is normal. So I heeded his advice and took out the dipstick and it did actually feel like a constant suction. If my AOS is bad, then that would definitely be why my CEL is on.

Does anyone know anything about that method or has tried it? What other way can I determine if I have a bad AOS for sure? Thanks in advance.

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Old 02-05-2009, 04:48 PM   #2
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If the light came on again, you need to recheck the code. It may be a different code this time.

I had an intermittent CEL that was the result of a single O2 sensor. Sometimes on, sometimes off.

Have you considered taking it to a shop?
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Old 02-05-2009, 06:11 PM   #3
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The code is just giving me a bad throttle valve or intake leak right now. The O2 one went away for now.
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Old 02-06-2009, 07:14 AM   #4
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Quote:
Originally Posted by Viper5
The code is just giving me a bad throttle valve or intake leak right now. The O2 one went away for now.
If you can, list the specific error codes you are getting. We can do a much better diagnosis this way. Without the exact error codes we are just shooting in the dark.
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Old 02-07-2009, 11:37 AM   #5
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P115
Porsche fault code 13 - heating power os2 ahead of cat. c. bank 1

P0507
Porsche fault code 32 - Idle air control system
exceeds limit value

These were the two that were originally there. The previous owner informed me that the P115 will come on intermittently but he didn't know anything about the P0507 which is the one currently there right now.

In summary:

Action
cleaned off the throttle valve and put it back.

Result
CEL went away but then return very shortly thereafter.

Action
removed oil dipstick

Result
slight constant suction inside (bad AOS?)

Action
start car

Result
thick smoke is NOT present in exhaust (good AOS?)

Action
Disconnected tube from AOS to air intake part#996 107 146 00

Result
inside of the hose, there were particles of oil. Not a thick stream, but just some dark dampness. I put a q-tuip in there and it is NOT drenched in oil, but it does turn dark where it is rubbed up against the hose. It's like a light coating of oil, but very light.
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Old 02-09-2009, 09:17 AM   #6
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PO507 is a high idle. Could be a sticking throttle body or intake air leak. Look for loose or torn vacuum lines, loose or torn intake tubing or clamps, torn AOS bellows, bad gas cap, bad oil filler cap or tubing.
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Old 02-09-2009, 02:19 PM   #7
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Everything seems to be on secure. I don't think there is anything torn either. How obvious would it be if it was? I know I have a leak somewhere in my coolant because it keeps dropping down when I drive it, but only then.

Scratch that about the coolant leak. When I unscrewed the cap, the pressure differential caused the level to rise to normal again.

Last edited by Viper5; 02-09-2009 at 02:31 PM.
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Old 02-10-2009, 07:40 AM   #8
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There are about 25 possible places for an intake air leak. most are not easy to spot. Start by checking your gas cap and oil filler cap for cracks, bad o-rings or obsolete part #s. Get it up on a lift and inspect your oil filler tube for cracks and AOS bellows. Re-trace your steps when the throttle body was removed to make sure nothing was overlooked or knocked loose during the process. Inspect all the little vacuum lines for cracks/leaks. It is there somewhere. Some guys use a little propane around all the intake fittings with the motor running. If you hear an increase in revs it will indicate a leak location. As you know propane is pretty flammable and I have been seared by a propane flash fire before so it is not my method of choice but it does work.

The good news is that an intake air leak is usually an inexpensive fix if you DIY. It just takes time and patience to track it down. Good luck!
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Old 02-10-2009, 10:34 AM   #9
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I did run over an opossum shortly before the light went off. Maybe it hit something and knocked it loose. The only reason I didn't think anything of it was because it gave me an O2 sensor error as well (which isn't currently there). I guess I was thinking that since this guy fixed it when there wasn't any leaks, it could be the same situation:

http://www.renntech.org/forums/index.php?showtopic=23455&pid=124869&st=0&#entry124869


Last edited by Viper5; 02-10-2009 at 10:36 AM.
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