Cutting out catalytic converter- how to

[bcviper123]

I pulled my side skirts off today and i have a buddy with a mobile welding unit coming over to cut the cat out and weld in a piece of pipe. Any pointers from you guys? What's the pipe size? 02 sensor need to be relocated?

[AndyMac]

You only have 1 o2 on either side since it's OBD1, and they are each located in the exhaust manifolds. No need to move them. The stock pipe is 2.5 inches. It's a pretty straight forward procedure, just make sure to tack the new pipe in place then set your side skirt back on to make sure the exhaust is situated correctly in the skirt opening.

[bcviper123]

Will it throw a check engine code?

[AndyMac]

No, the ecm has no way of knowing they are gone. (ie no rear o2's)

[Darth Menace]

not trying to rob this thread, but would a 98 gts throw a code (rear o2 sensor)

[AndyMac]

Originally Posted by Darth Menace

not trying to rob this thread, but would a 98 gts throw a code (rear o2 sensor)

Yes, it would. Your rear o2's are only there to monitor the condition of the catalyst. When you remove it, the ecm thinks the cats are toast and throws a P0420 code. There are a few ways to get around this, not too hard.

[Darth Menace]

sounds scary, but tempting.

[dirtbag]

Not sure about anyone else, but I used a Lynx 4 Crosscut saw.

[Able1]

I used tec screws to hold the exhaust pipe in position, then installed side seal to make sure pipe was aligned properly, removed side seal and exhaust pipe from car welded pipe joint, removed screws welded up holes left by screws, replaced exhaust and side seals. If you tack weld pipes together and they are wrong you must grind the tacks off to make changes. Also if you are welding on the car you should disconnect your computer.

[bcviper123]

I removed the pipe at the header and did the welding off the car.

[Jack B]

97 and 98 should not throw a code. I am running a catless 97. The 99 is where it became an issue. I am now running.a 98 PCM, Neither PCM ever threw a code. Even when I dynoed i would remove the OEM O2's and no code.

Originally Posted by AndyMac

Yes, it would. Your rear o2's are only there to monitor the condition of the catalyst. When you remove it, the ecm thinks the cats are toast and throws a P0420 code. There are a few ways to get around this, not too hard.