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The smoke can cause bad cats but not the other (archive)
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Posted by Rainman on August 26, 2001 at 01:22:13:

In Reply to: Could bad cats cause smoke? back pressure? help! posted by tom on August 25, 2001 at 21:57:50:

way around. If its too rich it will melt the cats and you'll see black smoke. when the cats break up like in the picture then they rattle and can clog the exhaust causing a big increase in back pressure.And a big loss of power as well.However usually something else triggered it to begin with. It has to be getting too much fuel to the cat to begin with.
I can hear a small but consistent (ceramic?) rattle when I first startup and gun the engine. I then can observe moisture around each exhaust pipe outlet. What happened to you when you discovered your cats were bad?????

Engine light comes on intermittently @ low rpms, goes out above 2400rpm. Just sync'd the DK's. Runs better, but still get the Lambda (Emissions) fault when ck eng light illuminates. O2 sensors just replaced--better, but still no fix.

Thanks for your input, this msg board is a great resource!!
Tom '90 750iL 170,000




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