msteiner805

Hi Everyone,
In doing a transmission-out service, I happened to get a look at the Secondary Air Injection Check Valve and I'm not sure what to make of it - there's quite a bit of oil on it.

What could be causing this? I'm not too familiar with the vacuum system on the 996 just yet - but it looks like the source of the oil is coming from the throttle body???

Thanks,
Mike

Ahsai

The is NOT the SAI check value, which is gray and has an electrical connector to it.
The valve is a one way valve that only lets vacuum into the vacuum tank (the black round canister on the right of your photo).

I agree with you that it looks like the oil is from the throttle body. Do you have oil accumulation at the bottle of the TB where it connects to the T-plenum? What's the crankcase vacuum level?

Ahsai

https://rennlist.com/forums/996-foru...omponents.html

Your vacuum valve is relocated but functionally the same.

DBJoe996

If your AOS is going bad it causes a lot of oil to be in the intake system and various vacuum hoses/check valves will have oil just like that. It may be just the start. That check valve is on the vacuum system. How's your oil consumption? See this picture for vacuum line routing. You can see it takes vacuum from the intake manifold.

msteiner805

Thanks Guys!
This was the part I found in the diagrams: http://www.pelicanparts.com/More_Inf...110-950-02-OEM

Do you have oil accumulation at the bottle of the TB where it connects to the T-plenum?
I will have to check this... not sure how.

What's the crankcase vacuum level?
I haven't put a meter to measure the vacuum yet, but, there is a strong change in engine note/idle when I remove the oil filler cap.

Mike

msteiner805

Thank you!
Oil consumption seems high in the 250 miles or so since I purchased the car... I got it fairly cheap and in rough shape (shot transmission among other things). So I'm in the process of bringing it back to full maintenance.

Sounds like I should replace the AOS then... FYI - 105k miles on the car and I have no service history.

Here's my other thread: https://rennlist.com/forums/996-foru...-ring-diy.html

Mike

Ahsai

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msteiner805

Hi Everyone,
I Just ordered a new AOS.
At the moment, I have the transmission out of the car (doing an IMS, RMS, clutch etc) and was wondering if I should try to replace the AOS from the rear of the engine? Is replacing it from the rear quicker than if I do it from the front?

Thanks,
Mike

Ahsai

It took me less time to do it from the bottom only but it's still a pain in the a$$.

msteiner805

Hi Guys,
So I replaced the AOS, and, completed the RMS and IMS jobs at the same time. I checked the timing by rotating the engine by hand several times, and, the timing all lined up. This is a 1999 C2 so skipping teeth on the chain is unlikely given the 5 chain motor, but I had the cams locked and the crank locked at TDC during the job.

I Started the car today and it ran rough, but, at higher RPMs it was smooth. Then after about 2 minutes the check engine light came on, then, a little while later started flashing.

I plugged in my ODB reader and got the following:

Stored:
-P0300 = Random Misfire Detected
-P0306 = Misfire #6
-P0304 = Misfire #4
-P0305 = Misfire #5

Pending:
-P1319 = Misfire Emission Related
-P1318 = Misfire (Cylinder No.6) Emission Related
-P1316 = Misfire (Cylinder No.4) Emission Related
-P1317 = Misfire (Cylinder No.5) Emission Related


Looks like I screwed something up...

No cam position codes, so I think the IMS is fine.

So, something I may have done wrong: When I replaced the AOS, it spilled out coolant. I didn't replace the spilled coolant (was going to do that later on). The amount of coolant spilled was maybe 1-2 cups (if that).

I believe I got the connections to the AOS correct and I used worm clamps that I made pretty tight. Not sure what to make of this other than I uncovered another fault?

The car ran slightly rough when cold when I got it, but, it never had the CEL on... could it be that the replacement AOS made the root problem worse?

Any suggestions would be welcome.

Thanks,
Mike

Schnell Gelb

I am working on a similar problem so may be able to help.Your issue is Bank 2 ONLY. Since only those 3 cylinders are misfiring - what is a common factor to all 3 ?
You'll have to start with basics - ground points,vacuum leaks, connections on the coils, valve timing
Some of this is known only to you - what did you do that only affects Bank 2 ??
In my case I am so limited on time that if in doubt when I remove something ,I fit a new one. - coils, plugs,spark plug tubes& seals , Camshaft sensor ,Variocam Actuator&Solenoid. I try to do methodical diagnosis and have made many different diagnostic cables and use Durametric but time and accessibility are the big constraints .
Problems like this are difficult to begin resolving without Durametric info. to share on the Forum.
Good Luck.

msteiner805

Thanks,
What ODB reader would I need to get more specific codes?

I read on one thread that the variable timing solenoid might be going bad, and, that a more advanced code reader will say this specifically. It would nice to get as much info as possible prior to replacing parts.

Mike

Macster

Those are rich misfires.

If the VarioCam solenoid connection is bad (either you on purpose disconnected or by accident disturbed the connection while you were working on the car) this can result in misfires confined to one bank. Because the VarioCam system isn't working right for the bank the O2 sensor readings are off and the DME will adjust fueling to try to get the readings it wants and in doing so will go too far and misfires are the result.

Best carefully check the VarioCam solenoid electrical wiring hardware and its connection to the main harness is good.

Another possible explanation is the fuel pressure regulator has been disturbed in some way and fuel pressure is too high. The #2 bank might misfire before the #1 bank due to normal bank to bank differences.

Bottom line is last thing touched first thing suspected and swapping out a bad AOS gives one the opportunity to touch a number of things.

An off the shelf OBD2 code reader can read active/pending codes, freeze frame data, and allow you to view engine telemetry, for instance short/long term fuel trims, but it does not allow you to go deeper like the Porsche diagnostic computer allows, which would allow you to check camshaft timing variation (if any) and manually activate/deactivate VarioCam operation.

Ahsai

Any intake parts you removed while doing the job?

msteiner805

Macster,
This is good info. I used a wire brush while cleaning certain engine areas (caked on oil spots). I did some cleanup to trace an oil leak to the hose connecting the AOS to the top of bank 2. Is this the area where the vario cam solenoid lives? If so, I likely hit it too hard with the brush... I'll have to take a closer look tomorrow. Sounds promising...

Ahsai,
I removed the airbox... and that's about it. While working on the car, I also likely loosened and not tightened the coolant cap, or, the oil filler, or, the dipstick...

As a side thought - I'm thinking I have to bleed the coolant? Did I introduce air bubbles into the system by replacing the AOS?

Anyway, I'll update tomorrow after I check vacuum connections and the vario cam solenoid connection (need to find out where this lives).

Thanks,
Mike