Darn, code p0422 came back :(

golden1245

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After being diagnosed as being caused by a loose vacuum hose in the engine bay by a more experienced mb tech and fixed...my check engine light came back on. Again, on my obd ii reader it's giving me the P0422 code caused mainly by faulty catalytic converters. It can also be caused by engine misfires or engine oil leakage into exhaust valve guide seals...

Based on your experience is the code mainly caused by faulty cats?
 
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golden1245

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Hey Olly, thanks very much for the reply. I just pulled off the red "kompressor" plate and looked into the spark plug area and found a small puddle of oil at the last spark plug. You can see it here:

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The rest are ok, with just tiny amounts of oil...

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No oil leaks on either side of engine.

Could this be what's causing the code?? I have noticed on two occasions where my car's power sputtered and surged for about a second. I didn't think much of it...is the real culprit of this a worn our valve cover gasket? Thanks a lot for your help Olly, I appreciate it!
 
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WG M-B

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Looks like the sealing ring has perished under the valve cover and is causing the misfire code. Replace the sealing rings/ valve cover gasket and clean the plug cap of oil residue
 
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golden1245

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Wouldn't that throw a misfire code instead of a catalytic convertor code? The engine runs and idles very smoothly 98% of the time. I'm pretty confused, ill be taking it back to the shop again for a diagnostic again free of charge because they couldn't figure it out the first time, but I want to go in with a bit more knowledge.
 
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Justin1600

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Take the cover off around where the diagnostic plug is, then take the multiplugs off of the Engine control Unit.
If you have engine oil in them multiplugs then you will need a new engine wiring harness, cam magnet, blocker loom and maybe control unit if full of oil.

Not seen this much though on a W202
 

WG M-B

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If that plug cap is full of oil it will cause problems. I wouldn't star looking too much into anything before you get number 4 firing correctly.
When black c55 remarked about oil in the loom he did not mean to check there.
It's best to unplug the lower oxygen sensor and look for oil in the connection there.
 
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golden1245

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I've read from one of Olly's past post that it could be condensation...or blackened water?

I'll stick a q-tip underneath there tomorrow to see what it is...
 

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