Pairing up old catalytic converterwith new one

[duster1979]

I've got a 1995 Crown Vic with a converter that leaks exhaust into the cab. I need to get it taken care of, and don't mind forking out the money for one new converter. But will pairing up a new converter with one that has 212,000 miles on it and is likely somewhat clogged a good idea?

I don't really want to replace both right now as I just bought the car and want to give it some time to make sure it's going to hold up for awhile before spending that much in one shot.

Any advice is appreciated, thanks!

[jdmccright]

I'd just replace the one cat for now. As long as you have no trouble codes coming from the OBD system, there should be no problems.

As far as I can research, your car is still OBD-I, meaning that if you have dual cats (really?) you only have oxygen sensors monitoring the exhaust before it enteres the cats...no post-cat sensors. But let me know if I'm wrong. The more typical (and cheaper) scenario is a Y-pipe from each exhaust header to one larger pipe with a single O2 sensor feeding a single cat. I have seen what looks like small cats coming from each header, but they are really just resonators. If they don't have heat shielding, they may just be that. But you might have a higher-performance option (police pkg, etc.) with a dual cat setup.

Obviously, to get the most performance you should replace both since then each bank will have equal backpressure, but you won't hurt anything by just replacing the one for the time being and then doing the other down the road. Hope this helps!

[duster1979]

I should have been a little more descriptive. It is a police interceptor with full dual exhaust, one cat per side, and it does have O2 sensors both upstream and downstream.

Regardless, you have answered my question. Thanks!