Originally Posted by oil_film_movies
Originally Posted by parshisa
Failed cats tend to fall apart and ceramic powder is being pulled back into the intake. It all leads to abrasives in the oil and causes damage to the cylinder walls.
Pulled in via the EGR? I've never heard of cat powder traveling up the exhaust pressure gradient and getting solid material into the engine.
Any other references on this issue you can give us? Links maybe?
Altima 2.5's were known for it. That said, I've never heard of any other engine doing. But I'm guessing any engine with a catalyst integrated into the exhaust manifold could do it, particularly if it skipped a physical EGR system and used VVT instead for the function.
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All this talk of cat failure. Remember there are upstream and downstream O2 sensors surrounding the cats to test their performance as you drive, so if you're not seeing a Check Engine Light OBDII code for it, its probably doing allright. Up to 80,000 miles, with that OBDII code, they will replace sensors and/or cats for free. Thank the EPA for that law.
True. But. My '99 had a dead downstream O2 for I don't know how long--I was playing with Torq one day, decided to see if the sensors were lazy, and found the downstream was dead flat at zero volts. I put a sensor on order, drove for several days (like several 50 mile each way highway trips), swapped the sensor--and never a CEL. New sensor had proper downstream voltages on Torq too.
I'm not complaining, but this car is plain not behaving properly.
That out of the way--I wouldn't mess with the cat unless if downstream sensor said the cat was dead or if I thought the cat was plugged or rattling.