I have a 1990 XJS convertible. This is the last year that emissions are needed in GA. Will taking off the catalytic converter improve performance ? or gas mileage ? The car was always running hot. A new radiator and fans fixed that. The mechanic said removing the catalytic converter would help also...Thanks-Roy

 

If the converters are clogged then you'll notice quite an improvement. If they are not clogged you notice very little improvement

Cheers
DD

 

I don't really know if it helps or not. I have a 89, and I took them off to replace my manifold gaskets, and was hard pressed to believe the car can run at all with that mess of stuff in there. I took a rod, and drove it into the material inside, and surprisingly, with not too much effort, it all came out. Put them back on the car, but really couldn't tell it made it run any better at all.

 

Doug, How do you determine if they are clogged ?

 

You will need a pressure gauge and some adapters. There is a large plug in the top of the rear mainfolds that hold the heat shield on. I'm not sure what size it takes, but you can install a pressure gauge to that hole, and if I'm not mistaken, you should have very little back pressure on the manifold. If its over 2psi, you most likely have a restriction.