A funny thing. O2 sensors and bolts in the 01(-04?) pathfinder

[ifyaknowatimean]

In my pathfinder, there are 4 )2 sensonrs (standard). I know the purpose of the first 2 is to determine the air fuel mixture and get it as close to 14.7:1 as possible. However, I was fairly certain that the second set of O2 sensors was to determine the efficiency of the catalytic converters and make sure they are functioning properly. Obviously, this isn't so, because my second set of O2 sensors are before the cats. What is their purpose???Additionally, does anyone have any idea how to get off a nut that is so rusted it no longer fits the same size ratchet? I tried the impact wrench, but like I said, I don't have a ratchet head that fits the damn thing, so that didn't really work. Any ideas? (This bolt is on the manifold to cat converter pipe connection where the gasket is, I was replacing my gaskets because they're ripped up, and of course I got stuck)

[burns9189]

THE FIRST O2 SENSOR IS A HEATED O2 SENSOR AND HAS 4 WIRES OUT OF IT IT MONITORS O2 LEVELS IN THE EXUAST (..sorry for caps)

For the nut try a grinder if you have one a s*** load of rust penetrate ...it happens there a b**** dont forget to use anti sieze when you put the new one in or the next time will suck more than this time .

[miamiheat3332]

to get mine now i used an adjustable pipe wrench and a hammer. works wonders, maybe vise grips and a hammer will work too.

[Empty V]

In my pathfinder, there are 4 )2 sensonrs (standard). I know the purpose of the first 2 is to determine the air fuel mixture and get it as close to 14.7:1 as possible. However, I was fairly certain that the second set of O2 sensors was to determine the efficiency of the catalytic converters and make sure they are functioning properly. Obviously, this isn't so, because my second set of O2 sensors are before the cats. What is their purpose???Additionally, does anyone have any idea how to get off a nut that is so rusted it no longer fits the same size ratchet? I tried the impact wrench, but like I said, I don't have a ratchet head that fits the damn thing, so that didn't really work. Any ideas? (This bolt is on the manifold to cat converter pipe connection where the gasket is, I was replacing my gaskets because they're ripped up, and of course I got stuck)

Your position 2 sensors are not before the cats, they are definitely after. I use an adjustable wrench to get mine out but we don't have any rust problems out here in so-cal.

Billy

[Pwnin O'Brien]

Obviously, this isn't so, because my second set of O2 sensors are before the cats. What is their purpose???

Those things that look like catalytic converters after the downstream O2 sensor are actually resonators, not catalytic converters. Although they look exactly like cats, they contain no platinum and they are not emission-related. Your catalytic converters are bolted directly to the exhaust manifold. The bolts you're trying to remove, those are bolted directly into the cats.

If you can't get the bolts loose by soaking then with some lubricant then you might want to try applying some heat to the bolts. You may also be able to drive the vehicle around for a little bit to let the catalytic converters heat up and then try backing out the bolts; be careful though because everything under there will be hot!

[Empty V]

Those things that look like catalytic converters after the downstream O2 sensor are actually resonators, not catalytic converters. Although they look exactly like cats, they contain no platinum and they are not emission-related. Your catalytic converters are bolted directly to the exhaust manifold. The bolts you're trying to remove, those are bolted directly into the cats.

If you can't get the bolts loose by soaking then with some lubricant then you might want to try applying some heat to the bolts. You may also be able to drive the vehicle around for a little bit to let the catalytic converters heat up and then try backing out the bolts; be careful though because everything under there will be hot!

Also remember when using heat to remove a bolt you don't want to heat the bolt itself, you want to heat the threaded opening that the bolt screws into. If I'm wrong please correct me.

Billy