FYI: Cats and O2s

[hillsjeep]

Originally Posted by Rodgebone

it very well could Phil but before you spend the money make sure the wiring to O2s themselves are ok...make sure the upstream wiring isnt so brittle its broken the wire....i had a similar problem on our TJ and found a broken wire INSIDE the connector at the upstream O2...make sure you pull the wires out of the connector to check them...and as Grant states you can insulate them will its apart...barring that, get a new downstream unit and go from there

Cheers mate, will do.

[hillsjeep]

Well I thought I'd start with the downstream O2 sensor as the upstream was only replaced about a year ago. It didn't look too bad but I cleaned it with petrol & a toothbrush. checked the wires and cleaned the plug too. I cleared the codes and went for a drive and the "21" code has not returned. I also think it idled a bit smoother.

I'll keep an eye on it and get a new downstream sensor when my wife gives me some more pocket money

[AussieRCBasher]

i took my cat out and it was nice and clean too but it had a hole in it anyways. also ive been told by exhaust places that cats really need to be replaced ever 100k or so. so thye may look clean but they are really quite clogged.

[Rodgebone]

also ive been told by exhaust places that cats really need to be replaced ever 100k or so. so thye may look clean but they are really quite clogged.

if you can see straight thru the substrate then its not clogged - pure and simple....HOWEVER, the substrate material can become fouled with a coating that contributes to its effectiveness towards interacting chemically with exhaust gasses....the cat is meant to heat up spent fuel exited from the engine and burn it off thus lowering harmful emissions into the atmosphere...if it were not able to do this the downstream O2 would pick that up and set a code (its main job is to monitor emissions coming out of the cat)

aussieRC - exhaust shops tell you this to get a job out of you...in theory they are correct but in the real world its just not that common for a cat to "wear out"....if it were youd see a helluva lot more downstream O2 codes

[Grant]

Best way to check the operation of your cat is get it hooked up to a test rig that will give you emission output from the sucker / test probe that goes into your tail pipe (any good exhaust / tuning shop will be able to do this test for you) this test will also give you an EPA tested certificate (handy to have in glove box) if you want it.

Mine was done when I had it on the dyno

[john_char]

I just took both 02 sensors out. They have different plugs, so they can't but swapped over.

John

[fisher]

Originally Posted by john_char

I just took both 02 sensors out. They have different plugs, so they can't but swapped over.

John

True but the sensors themselves are the same. If you just cut the wires they are the same colors on both plugs so you can always just solder them on to the different plugs.