2001 Sport 3.0L Auto 4x4... 240,000 stock OEM cats

Ok remember that I'm still new to this rig and the world of Mitsubishis...so if this is a stupid question I'm sorry!

What lead us to this point....

We already replaced the 02s twice on this beast. The first time was because the Previous Owner drove around for lord knows how long with codes for the EGR and O2s. The second time was due to the P0431 code and the tech finding irractic info on the scan tool for both O2s. So we opted for a second set of o2s. This helped for 150 miles & then the P0431 was back. The guess its because the PO did most of the damage to the cat by driving on bad o2s before we got it. So bad cat was the final verdict. Obviously once the cat is bad its only a matter of time before it plugs and either breaks up and dumps into the downstream cat and muffler or causes nasty backpressure and hurts the motor. So it has to be fixed sooner rather then later.

Good thing the precats are sold as "bolt in" individually. I refuse to do a weld in. Bolt on only! I read that using a budget bolt in will not last long (less platinum). So its top of the line aftermarket or OEM. Well OEM is ridiculous price wise. So I start looking at aftermarket.... well one guy on another forum mentions that the aftermarket units use crimp bends versus the factory mandrel bends... I'm not trying to restrict things further. So then I'm leaning back to factory... Then I start thinking... if the Drivers went out due to PO neglect isn't the passenger side soon to follow.... Then I will really be dropping some $. As it is we don't really have the spare cash to be dumping more into this after everything else we have had to do since November.

So I factor in what I'm planning for the truck in the next little bit. I plan to add a CAI for its minimal gains and add a flowmaster & shorten the exit pipe to infront of the tire... Yes for the ever so "slight" performance gain, but mostly for a better sound and to reduce the size compared to that MASSIVE factory one. Well replacing the bad cat will pretty much eat the budget I had to do the upgrades. So with that in mind my Dark side pipes in... just delete the precat dummy. Use the cash instead on the new exhaust. All the other cars in the family have a cat delete for performance. We have the x pipe on the Mustang GT (with mil eliminators), A straight pipe bolt in on the 87 firebird and Fiero... Why waste the $ on new precats.

So if I listen to my dark side and remove the factory monitored precat, what about the CEL light you ask. Well folks trick the ECM with a doubled up spark plug non-fouler. Pulls the rear most post cat o2 out of the exhaust stream enough to fool the ECM into thinking the exhaust is just fine. You don't mess with the front o2 as it suposedly talks to the ECm about what the engine is actually doing. They say the rear most "after cat" o2 basically monitors the cat's cleaning of the exhaust. So with that said, in theory, I could fix the CEL issue and eliminate the precats by adding non foulers to the "after cat" o2s. Then I could take the money I "would have" spent on the cat and have a shop make a bolt on "catless" off road version with O2 bungs and add the Flowmaster. Yes I shop is not supposed to disable emissions equipment. If I tell them to basically design it so everything is a bolt on like factory. I can save all my factory parts intact to take off and on at will. So with the bird, the story was to have the straight pipe to put on when "drag racing". With the Sport, I will tell them I want to be able to take off the cats when off roading so I don't crack a cat on some rut or rock while playing. Chances are it would end up cheaper. Then I could always go back to factory (new precat) "if" I want to sell it. Plus it would give me time to save up for the precat.

So now its time for you wise folks who have been there done that to tell me if its a good idea or stupid. I don't know much about the temperment of the Mistubishi's when fooling with Emissions equipment.
Is there any harm to come from doing this?
Will it tank my gas mileage, or make the truck run crappy?
Will it help with performance or just stay the same?

As always thanks you guys!

If you say you don't know what you're doing why would you think you should be redesigning the emissions system better than Mitsubishi engineers?

Emissions systems help keep the air clean, but they also keep the air/fuel ratio at optimum 14.7 depending on engine requirements.

Goggle says P0431 is bank 2. http://www.obd-codes.com/p0431

Not trying to redesign anything. I must have said something totally wrong? Emissions equipment was never put on any car to improve performance... it was added to protect the environment. You dont see any race cars with emissions equipment. But before you say it.... im not some kid thinking an oversized top heavy SUV is a race car. So there is no redesigning here. Just trying to bypass/replace a failing system component. I prefer not to pay top dollar for a replacement unless it is critical to to the drivablility of the vehicle. If the only harm from a precat delete is a CEL that I can theoretically turn off. Then there is no harm to the vehicle or its drivability. If there is a 1-2 hp bump once a Cai is paired with it great. If It stays the same... great. I'm not behind anything. Just ahead $ wise. As for the environment... the downstream cat is still functioning so it will probably stay for now. Again. Why everything will be a bolt on style. Mix and match my components.

So the long and short of my lack of knowledge is that I don't know how sensitive the tuning is on Mitsu vehicles. I know I can straight pipe a domestic (gm & ford) add in mil eliminators or O2 simulators and be fine. Add a Cai with it and pick up some hp gains. Never earth shattering, but something. I just wondered if the same was true on a mitsu vehicle?

Not sure what I said that made you think I was trying to one up mitsu? Sorry that I must have offended you. I must reread my initial post. I was just trying to make sure I was not going to throw the rig into ecm chaos getting 10 mpg or such foolishness. So much for looking for fora bit of understanding before one jumps off the proverbial plank.

You can pull the manifold heat shield off to check for a crack. They ALL crack eventually, my '01 manifolds were cracked at 65K miles. I don't remember what code mine threw, but i don't think it was the same one your getting.

I will check this. Did you hear an exhaust tick to clue you in on the crack or was it just a code that indicated the leak? Once you got the code was the crack obvious? I was planning to SeaFoam the rig in the next little bit. Any leaks should light up with smoke from the SeaFoam. At least this was a good check to find exhaust leaks on the Firebird. (It would roast the cheap manifold gaskets in no time.) Seems we were always looking for a leak. We had to switch over to thicker "header" gaskets and then it was golden...

I had a mechanic checking the Sport out and he never mentioned finding a leak. Though I did not tell him to check while he had it.

And yes I trust him to not be trying to get a $$$ repair. Only guy I know who did not charge me for a repair when he screwed up and misdiagnosed. It was a leaking transmission. He had me do a pan gasket first and it still leaked. I can't tell you how many hours he wasted trying to track the leak. It continued and had him and his tranny friend stumped. They knew it was trying to overheat, but why? They were thinking it needs a aux trans cooler.

In the end, I figured it out thanks to google. Ended up it was a plugged tranny vent and the fluid was coming up the dipstick. He unclogged the vent cleaned up the rig and charged me nada... Most places would still charge you a diagnostic fee and a time for the cleaning of the vent... I'm not sore about the forced tranny pan gasket, as it really needed a trans service to verify all was well inside after my daughters boyfriend got it stuck in 3 feet of mud. (hense the clogged vent)

I stumbled on my cracked manifolds while removing the heads to fix bent valves, there was no noticeable tick(any more than usual). I saw the cracks and thought "there's my check engine light cause". Now that i think about it, my trouble code was probably p0420 catalyst efficiency below threshold. I solved the problem with headers from RPW. <img src="/forums/images/graemlins/smile.gif" alt="" />

What did they set you back? How bad was the install? Just in case thats my issue...

I think they were just over $600 shipped from down under, in 2007. The fit was not perfect, i had to cut and re-weld the flanges to get them to sit flush with the supplied y pipe flanges. I had a 2.5" hi flow cat laying around, so I used that. Picked up a Magnaflow muffler and then just dumped it in front of the rear axle. It's a little loud, not too bad. I mounted the two upstream o2 sensors in front of the cat, and the two downstream cat monitors behind it. There are no codes no check engine light, but the egr self test won't complete, due to egr block-off. The headers don't come with a bung for the egr tube.

Video for sound.

Couple pics, there's silver ceramic coat under the baked on dirt. <img src="/forums/images/graemlins/smile.gif" alt="" />