Whether you replace it with the pipes or not depends on price, ease of access, and how the system is assembled. You will have to look at it to see if it is welded. Back in the 1970's GM catalytic converters were bolted on and were easy to replace, but those flanges caused more trouble than the converters did. They often rusted to the point they would pull off and fail to hold the pipes tight enough to seal. Systems that are welded need to be cut apart. If the replacement comes with more pipe than was removed, you may be able to expand one and slide it over another, then use a standard exhaust pipe clamp to hold it on. If the new converter is just the body with no pipes, you have to be sure to cut the old one out and leave enough pipe to reach, then it will have to be welded back together. Only a wire-feed welder works for that. A stick-type arc welder will burn through the thin metal. Brazing is not strong enough unless two mating pipes slide into each other first. The body is made of stainless steel, and the pipes it comes with usually are too. That is harder to crush with a clamp than is regular steel exhaust pipe. Stainless steel is harder to weld too.
If you replace the converter with a straight pipe, you will have what you have now; an ineffective converter that does not do anything, and the check engine light is on. Both oxygen sensors will "see" the same thing, so the computer will know no change is taking place in the make-up of the gas. Replacing the converter with a pipe is a real lot of work to end up with the same thing you have now.
Be aware too we read a lot here about people having repeat or new problems when using universal aftermarket catalytic converters. Their efficiency was not monitored on 1995 and older cars, so you never knew if they were working properly. Anything will work on those cars. A lot of shops will not replace exhaust parts with anything other than what comes through the dealer, especially if they are in an area that has emissions testing. A universal converter can work fine on one car model, but when used on a different model, it may not pass the emissions testing.
Thursday, June 29th, 2017 AT 7:21 PM