Originally Posted By: JHZR2
Originally Posted By: Jarlaxle
Originally Posted By: JHZR2
Originally Posted By: Chris142
it may be a bad cat. especially an aftermarked cat
Agreed. My 318i doesnt even have EGR. Failed NOx once, replaced it with a Magnaflow, barely passed. Replaced it with an OEM one, and passed with flying colors...
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/915639
ONLY EVER BUY OEM if you plan on doing anything besides dumping the car.
I learned that at my own expense. The aftermarket cat was barely good enough to improve numbers compared to my OE cat which was not converting NOX. New OE, NOx was at 7. All the other measured items had substantial improvements percentage wise but nowhere near the swing in number values.
My Cherokee passed two tests with a cheap part-store cat (Walker, I think) without a problem. And note: the OP's car PASSED twice with the aftermarket cat in place.
Wonderful. Dyno tests or just idle sniffers? Make sure youre talking apples to apples and posting numbers before drawing conclusions. My car passed with one of these too. Two years later, not so much. OE converter immediately took it from thousands to single digits, simple as that.
IM-240 roller test (tougher than the OP's 2-speed test), passed easily both times. About 65,000 on the cat the second time. Considering the one I had lists for about $100 and an OE cat could run $500+ (if it hasn't gone NS1), it's probably cheaper to use the cheap one even if I DID have to replace it every 2 years.
My Caddy has over 100K on its catalysts...passed its last emission test (also IM-240) last year, about 10% the allowable emissions. (Not bad for 542ci and 3x the factory power...)