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All good advice, but a couple of "possibles" for you Posted by Mark in Marine [Email] (#1837) [Profile/Gallery] (more from Mark in Marine) on Mon, 1 Jul 2019 07:09:41 In Reply to: V6 reoccurring P0420, fdw201 [Profile/Gallery] , Fri, 28 Jun 2019 09:50:15 Members do not see ads below this line. - Help Keep This Site Online - Signup |
K W and Don have you mostly covered - but there are a couple things you can check out.
An exhaust leak at the joint closest to the rear O2 sensor can produce issues like this, depending on the ECU logic used to compare the upstream and downstream O2 signals. So If that's the bad joint, I would try to fix the leak if reasonably feasible.
The other item to try is running some Techron(R) concentrate through your gas. Maybe at a little higher than the recommended ratio (slightly less gas per bottle). This could seem like "FuFu dust", but there's real chemistry at work (I am a chemist). The first thing is that it will clean injectors and even some intake valve deposits, depending upon how much there is to clean up. Secondly is that very small amounts of unburned fuel will make it to the cat over your cold starts, and for a number of BMW owners (including me) this has postponed the impending cat replacement.
I'm speaking from my own experience with a 2005 BMW at 203K with one of two cats gone'lazy' - replacing those cat(s) is WAY more effort than on a SAAB 2.3L, since the inline 6 'nests' its two exhaust manifolds with the cats built into each of them. From WIS the V6 cat R&R is more awkward than the 2.3L, but pretty 'clean' by comparison to a lot of other cars.
Feel your pain - hope this helps.
Mark in Marine
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