bmw 328xi 2008

[nabil1995]

i have bm328xi 2008 n52 engine it's been throwing codes P0420 P0430 with the service engine soon light in February I replaced catalytic converters and one of the O2 sensors and I replace the camshaft sensor and the crankshaft sensor and I replace the gasket valve cover because it was leaking and I replace the electrical water pump and the thermostat and I replaced a mass air flow sensor and from a month ago I did a smoke test and found two leaks so I put new seals did the test again no leaks were found
and I replaced the spark plugs and coils last year

[MauiM3Mania]

Moved from General BMW Discussion sub-forum.

[MarcoZandrini]

Please use punctuation and write sentences that are 15 words or less. Why? You loose the readers attention by writing a string of words.

[shadowpuck]

Please use punctuation and write sentences that are 15 words or less. Why? You loose the readers attention by writing a string of words.

+1

[bmwdirtracer]

Hi Nabil, and welcome to the forum.

Your catalyst efficiency codes are certainly something to be concerned with. How MUCH of a problem is probably determined by WHERE in the "usa" you live.

You have , unfortunately, made a few errors, in trying to fix this issue, and I hope you'll understand that we're trying to help. I'm as unable to deal with zero punctuation as the guys above, so please avoid that.

Most importantly, though, you've got to quit shotgunning expensive parts, without better diagnosis.

Sure, catalysts are OCCASIONALLY the cause of catalyst efficiency codes - but the vast majority of the time, there's an underlying issue, which is causing the secondary O2 sensors to decide that the catalysts aren't doing their job correctly.

Oil or coolant in the exhaust will cause this. (Failing crankcase vent? Coolant leaking into a cylinder?)
Too much unburned fuel will cause this (dripping injector or two?)

Bad primary or secondary O2 sensors? (You replaced thousands of dollars in catalysts/headers, but only one O2 sensor? WTF?) NEVER replace cats without replacing the O2 sensors!

MAF? Why did you replace the MAF? Did you have a code for that, or did a good tech see that the live data was bad?

I'm hoping you didn't replace the thermostat and water pump trying to fix the catalyst issue?

You nee a better diagnostician: someone who can watch live data on a top-of-the-line BMW diag computer, looking for anomalies. Personally, I'd have sent the injectors to RC Engineering for cleaning and testing, and replaced the O2 sensors, LONG before I threw cats at it. If a good diagnostician hasn't done testing, are you sure that the secondary O2 sensors are even plugged into the correct bank of cylinders? Because THAT would certainly cause cat efficiency codes, and the fix would require ZERO new parts.