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Old 05-23-2019, 12:38 PM
mejim707 mejim707 is offline
Join Date: Jan 2018
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Originally Posted by ard View Post

How come new cars dont need that? Somehow the car got to 200k without needing it....all of a sufdden the O2 sensor bung didnt shorten.

(and I dont think it is a spark plug anti-fouler... )

Ever think that there is something going on with your air-fuel ratio, that is choking up the cats and giving that code???

Or are you a 'I just fix CELs, dont dig deeper than that' kind of guy?

PS post your long and short term fuel trims,bet the car is running rich- not rich enough for a code, but rich enough to foul the cats

The car isn't running rich that I can see. No codes, no smog, same fuel milage, just cleared emissions and runs perfect. At idle you can't tell the car is on if you're not looking at the tachometer.

This sort of thing could happen due to the valve cover failure I noted at the beginning of this thread. That was causing the p0012 code (running rich) and lead to a slightly fouled catalytic converters thus leading to the p0420 and p0430 codes much later on. I replaced the valve cover with a new one, but it doesn't take long running rich for the cats to foul. Thankfully this was not an issue for a long time. Typically p0012 is vanos related, but the high pitched whistle coming form a failed valve cover crankcase vent valve pointed to only one possible solution, replace the valve cover (my most major repair to date).

Catalytic converts also have a life expectancy. They do fail or start performing slightly "out of spec" over time. However, the emissions still pass so how bad are they really?

Definitely not a "Fix the cel" and move on type of person. I replace everything if it fails, and try my best to maintain this fine piece of machinery. But the sad truth is a $3200 repair, to replace the catalytic converters (yes there's two) on an 11 year old car is just not sensible. However much I love the vehicle, doing a $10 repair to save thousands is the correct approach.

I hope this helps.

2008 X5 3.0si
256k Strong
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