Hey all. I have an '04 C2 that has thrown a P0420 error - inefficient catalyst. I have read the O2 sensor voltages as the cat is indeed done

I am basically curious if it's the fault of a gentle AOS failture wreaking havoc on the cat over time. The video below shows what happens when I remove the cap. The cap comes off rather easily, but there is definitely suction and the idle changes smoothly (RPM's increase). Can anyone suggest if this is a sign of a failed AOS or not?

http://s23.photobucket.com/user/aero...37351.mp4.html

 

Anyone??

 

looks like innermix.

 

It could be, but I think you normally get more suction from a bad AOS than that, but that's a lot of moisture in there. The moisture could just be from short trips on a cold engine, which can also cause cat failure due to the rich condition of a cold start.

 

I agree, but with that much moisture it could be clogged causing less suction.
At this point I would suggest cleaning that stuff out and getting an oil change and re-setting/clearing the codes and go out for some long spirited driving, weather permitting. Then re-evaluate, at least you would know most of the moisture is removed and if the lite comes back on you would know it was truly a bad cat. I wouldn't let the oil get this much moisture in it again though.
As a second point, if there is that much moisture in the oil, you really need to check you brake fluid as the same thing can happen.

 

Do you get any puffs of smoke when you start the car? Take note if it comes out from both sides of the exhaust or just one.

As suggested above, definitely change the oil and see if there is the same crud on the coolant expansion tank. If that is the case, then you definitely have a case of intermix (oil and water).

 

Thanks for the replies everyone.

I already know the cat is toast - I have read the oxygen sensors both before and after the cat on bank 1 and can see that the car is having no impact. Bank 2's cat is working fine. I am just curious if the suction I am seeing is normal, or an AOS failure.

I do get a little bit of smoke coming from the bad cat side, only during the first moments of cold operation.

 

+1. That filler tube is very dirty.

 

I think he has that 'Vitamix Blender' option I've always heard about....

So that's where you put the ingredients!

 

The guidelines for P0420/P0430 are to if any aging O2 sensor codes are present to replace the indicated sensors, clear the codes and then drive the car.

If the P0420/P0430 codes come back replace the converters.

The engine's reaction to the cap removal is normal. It creates a big intake air leak. The DME will adapt though and the engine recover to about how it was running before you removed the cap. The moderate vacuum is normal. One failure mode is the AOS creates so much low pressure in the crankcase one can't pull the oil filler tube cap off against the pressure difference.

But either not all AOS's fail this way or the failure mode is transitory. So you can't use the absence of extreme low pressure as a sign the AOS is ok.

The stuff in the oil filler tube is what collects when the car is used for short trips and the engine doesn't get completely warmed up. The cold engine accumulates water -- combustion by product -- which when the engine gets warm turns to vapor and condenses at the top of the oil filler tube because that is the coldest place in the crankcase accessible to the crankcase fumes with the water (and oil) vapor.

I do not think the engine has an intermix problem but better safe than sorry. So to eliminate any intermix problem have the oil analyzed for among other things presence of anti-freeze chemicals.

If you find there is no intermix you should change the oil/filter and wipe out what you can of that goo at the top of the tube.

Then be sure to drive the car more for longer distances and get that oil hot, hot and hot. Did I mention get the oil hot?

And consider moving to a shorter oil/filter service interval too.