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Old 05-16-2015, 05:35 PM   #1
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AOS barb connector/fuel vapor recovery

So I've got about 750 miles since putting my engine back together and installing it. It's been mostly great, but as expected there can be a few odds and ends to address before one can call any major work a success.

I got a CEL a few days ago. It wasn't flashing and the car was running great, temps good, fluids good, etc so I didn't panic. Today I plugged in my laptop and used VCDS and the cable to read my codes (VCDS is the well known diagnostic/parameter tool for VW and other makes owned by VW, but all it does for a Porsche is basic OBDII stuff. VCDS rocks btw. I found out I've known Uwe for quite some time through an unrelated forum. His product is super cool and allows me the matrix brain dump for our Touareg).

I got three codes
P0410 - Secondary Air Injection System Malfunction
P0411 - Manufacturer specific code (turns out to be also SAI related)
P0455 - EVAP system: Large Leak Detected.

I have had some mild raw gas fumes in the car occasionally and eventually deduced it was my car and not the ones sitting at a light around me.

I did some searching and found discussion of P0410/P0411 and I'll need to run that one down. My SAI is hooked up and I hear it running when the engine is cold - I listened to it this morning in fact before I knew that was a code I would read later.

Since SAI is not related to the way a car runs I'm not in a panic but I will sort it out since I live in an area where emissions testing is via OBD II and codes like that will prevent the ECU from entering the mode that allows them to query which is the only way you'll pass.

I also did some searching on the fuel EVAP thing, and most links point to the front wheel well where the canister is along with the associated tubing and valves. I know a car can get a little crunchy after sitting with it's a** in the air for 7 months waiting for some love, but given my next statement I am thinking that it is engine compartment related.

I say this for two reasons. One is "Occam's Razor" - my next statements will support why I think the most obvious place is in the rear of the car. Two, if I go old school and review how charcoal canisters have worked since around 1972, they basically just collect vapors from the gas as your car sits. When you crank the car up again a line leading to the intake system sucks the vapors from the canister and burns them instead of releasing unburned hydrocarbons to the atmosphere. Super simple, basically never needs work and had no *$&# valves and connecters.

No matter how sophisticated Porsche attempted to make a previously caveman simple device, it should still have a vacuum line leading to the intake system.

You've probably been wondering why I tied the AOS to this subject. It's because I have an open barbed fitting on the top AOS hose that goes from the AOS to the intake manifold. With the barb fitting "open" the car idles like CRAP. On the first day with the engine back in the car I saw it and capped it with a chunk of fuel hose and a bolt (the very same one that kept my fuel return line dry for the past 7 months.

These pictures show the hose, and in one my digit is pointing to it. I have the super stealth cap removed for these pictures.





I feel pretty stupid after keeping track of literally hundreds of parts for the past half a year that I missed this. I've gone back over my notes, the pictures in Wyane's "101 projects for your pet rock" book and don't see where I pulled this line off.

I've also done a quick check of AOS threads to see if anyone mentions the barbed fitting but coming up with zip, nada.

I've literally laid on my trunk staring down into the top hole thinking I'll see a loose vacuum hose. I can't tell you how many times I have seen the starter ground cable and thought "aha! Oh yeah. Dammit".

So. Now if I take the issues as unrelated (still very likely), can anyone out there in TV land tell me what is supposed to be plugged in to the AOS barbed fitting?

For bonus points, can anyone verify that there is indeed some type of vacuum line going to the back of the car from the front that carries fuel vapors and if so where does it join the intake system?

I appreciate any input.
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Old 05-16-2015, 06:09 PM   #2
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Garage
Check part #12

Intake Distributor

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2003 Boxster S
| 987 Air Box | K&N Air Filter | 76mm Intake Pipe| 996 76mm TB | 997 Distribution T | Secondary Cat Delete Pipes | Borla Muffler | NHP 200 Cell Exhaust Headers |
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Old 05-16-2015, 08:13 PM   #3
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Good call Kram. I have no recollection of that entire line from the quick disconnect to the place in my pic, and starting at the top side isn't producing a thing. I'll jack the car up in the morning and start from the QD fitting

Thanks!
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Old 05-17-2015, 02:21 PM   #4
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Found it. Started under the car and worked my way up. The rubber part was tucked under the intake manifold.

Right a rain now.
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