Just another AOS? Or something worse...

[logray]

99' C2 w/~60k miles.

Car is burning about a quart every 3-4k. Added about a half quart today after about a 1 hour drive. Took it out to get some gas and the CEL came on. Some soot, a tiny amount of oil coming out of left exhaust tip below 4,5,6 for a while now.

Has been running very smoothly but all of a sudden idling a little rough, fluctuating. Cleared first occurance of CEL with PST2 then they all came back on except for the 8 misfire with empty tank and maybe a couple more but I would double check. Codes:

68 Cylinder 6 midsfire damaging to cat. converter

67 Cylinder 5 midsfire damaging to cat. converter

66 Cylinder 4 midsfire damaging to cat. converter

10 O2 sensor ahead of cat. conv. Cylinder (1-3)

18 O2 sensor ahead of cat. conv. Cylinder (4-6)

75 Misfire damaging to cat converter.

8 Misfire with empty tank

Going to do the oil filler cap suction test. Hoping it is just another AOS.

BTW, when it rains it pours, the govenator sent me a smog renewal letter today.

Advice welcome! :-(

[logray]

After clearing codes the first time here is what came up.

62 misfire emmisions-relavant

53 Cylinder 4 misfire emissions-relavant

54 Cylinder 5 misfire emissions-relavant

55 Cylinder 6 misfire emissions-relavant

75 misfire damaging to cat. converter

66 Cylinder 4 midsfire damaging to cat. converter

67 Cylinder 5 midsfire damaging to cat. converter

68 Cylinder 6 midsfire damaging to cat. converter

This time nothing about cyls. 1-3, which leads again towards AOS?

Did the filler cap suction test. Not having tested another Carerra I don't have anything to compare with, but I would rate the suction as moderate. With a VERY FIRM grip on a latex glove, it was very noticably being sucked into the filler tube. A slight to moderate amount of air noise wooshing in. Idle became even more sporradic, inclulding left bank of cylinders with cap removed.

Cleared codes a third time. This time it idled for about 10 minutes and NO CEL codes came on, no rough idle (although the moderate suction was still evident).

[dr914jr]

There aren't allot of ways for oil to reach the combustion chamber sounds like an AOS. You made mention of the time frame for consumption but how about the mileage?

[Loren]

Look for oil inside the throttle body (just remove the intake hose).

[logray]

There aren't allot of ways for oil to reach the combustion chamber sounds like an AOS. You made mention of the time frame for consumption but how about the mileage?

About a quart every 3000 or 4000 miles. OH, I forgot to mention I was cleaning the intake and noticed a little oily residue insde the intake plenum area... more evidence I guess.

[logray]

Look for oil inside the throttle body (just remove the intake hose). ?

Yep, each time I've cleaned it there's been a little, and a little more yet inside the Y-plenum behind the TB.

Edit: anything besides the AOS 996-107-023-55-M100 I might want to replace while I'm in there, boots, lines, clamps, etc?

Edited March 16, 2009 by logray

[dr914jr]

The AOS should come with the boot that connects the base of the AOS to the case. The boot should definitely be replaced but the lower clamp is a bit of a hassle. It the car a tip.? The job is much easier in a manual.

[logray]

The AOS should come with the boot that connects the base of the AOS to the case. The boot should definitely be replaced but the lower clamp is a bit of a hassle. It the car a tip.? The job is much easier in a manual.

It's a manual. I've decided to try the procedure without dropping trans. Also everything I've been reading here about the AOS failure matches what is happening on my car. I'm not getting as much white smoke as some describe, but there is some - primarily on cold start. Will post my results, new unit supposed to arrive tomorrow. It will be a late night!

[logray]

If you've never done one before, it takes about 3 hours to get the old AOS out using the non-manual-trans drop method. This is using the method described in this post.

The only other things I would point out in addition to the post above and you pretty much have a DIY for removal are:

- A couple things go without saying but should be mentioned, disconnect battery FIRST, remove airbox.

- To get my fat forearm into the rear inner left intake maniflold screw I had to disconnect the positive cable going to the starter

- Two of the hoses on the AOS were held by single-use crimp on clamps - and I had to cut the hoses off - so buying the screw-on hose clamp is a requirement, not an option in my case (heading to auto parts store tomorrow). While you're there buy another screw hose clamp for the new rubber bellows at bottom of AOS.

- Before removing any hoses on the AOS and the manifold screws on the inside behind the alternator, remove the screws holding the AOS onto the block, this is done under the car. This will free up the AOS just enough to get more play for a wrench in the tight space. Also helps when you go to remove the hoses off the old AOS.

- I had a HELL of a time removing the large hose clamps on the adapter tube running between the manifolds behind the y-plenum (the hose not attached to the TB). The screws for the clamp were litterly BEHIND the hose (apparently installed before entire motor assembly installed in compartment. I had to reach underneath the hose and without seeing what I was doing somehow turn a stubby phillips just enough to jimmy it lose by wiggling the manifold. This was the LAST thing I did, after removing all of the intake manifold screws. If you can't see the screws to turn the clamps on the rear hose adapter, I might recommend not attempting this method of removal and just go with dropping the trans.

The 986 DIY website was not useful for a C2 996 aside from just cutting the old rubber bellows instead of messing with the clamp. Basically get the AOS out of the way and then mess with the clamp. Otherwise the procedure is drastically different as far as how to get the old AOS out. Here is that link.

NOTE: it should go without saying that this is NOT a simple DIY, it is for the mechanically inclined ONLY.

Tomorrow goes the install! Should go much quicker as long as I don't forget any screws.

[dr914jr]

The post at 4am speaks volumes. I hope the install is easier than the removal for you.Just think of all the sweet sweet greenbacks you're saving. :)

[logray]

The assembly went much faster since I knew how everything goes together. However it still took about 2 hours.

I made one mistake and forgot to secure a clamp on one of the coolant lines, lost a gallon or so of fluid and had to deal with that after the repair.

Note the AOS needs the coolant running through it otherwise it will not function.

Now when I remove the oil cap there is a small amount of negative pressure and the engine idles a little rougher.

After the coolant issues sorted out and a few drive cycles I inspected the TB and intake - NO MORE OIL.

Oh and no more misfires, or CEL.

Let's hope that did the trick.

Thanks for everyones help!

[dr914jr]

Very nice Logray. Congrats!