Some of the many causes of this code include intake and exhaust leaks that introduce too much unmetered air into the system. Since that O2 in the pic above is the one that is reading too lean, I think I have the issue resolved.
I have a question on these 'hard' codes that need special equipment to clear permanently. Doesn't the ECU automatically clear/reset codes after a few starts of issue resolution? My plan is to just clear with my iPhone/Rev app, and then see what happens. However, if it comes back I am not sure if it is because it was a hard code or because I still have something to fix ? Any code experts out there?
And here is another pic of the failed gasket.
To be honest though, I might need to adjust those flanges for a perfect fit, a 3 bolt flange would fit more securely but would be very difficult to get at the third bolt.
I would have a closer look at that header. That gasket failure may well be the cause of the code, considering that the O2 sensor bung is too close to the flange, but have a look at the collector welds. See any cracks? I wouldn't be surprised if there's another cause for that code. The best way to tell if you've solved the problem is to reset your adaptive values with a tool that reads and resets BMW proprietary diagnostic codes.
The black spot on the heat shield is soot from the exhaust leaking from that header to cat-back flange.
Under a constant WOT condition, certainly there is pressure. However, in other conditions air can be sucked in. In this case the O2 sensor is really close to that leaking gasket, even though it is actually upstream.
Last edited by mini_racer; 03-08-2011 at 12:40 PM.
Thanks Eric and damn, looks like I do need to get to a shop. All welds look good, but my inspection was somewhat limited as the header is still installed.
I am still a little concerned about the flange mating, with the new OEM 2 layer spring stainless gasket installed there remains a small gap between the flanges that the gasket must fill, of course this is right where the leak was found. So yeah, technically the gasket failed, but it had help.
Even if a Victor Reinz gasket was used, it is a 2.5 flange mating with a 2.25, there's not much surface area to seal. Consider a 2.5 flange and transition section in place of OEM, it will also smooth that reversion step it has currently.
On the header you have, an inspection from the head flange side will show more than can be seen at the primary tube exit side.