XJS Tech Question

[jimbeaux]

1995 XJS 4.0L - Bad mileage, a slight "miss" at idle, no discernable pattern. OBD II scanner codes P0420 / P0430. I believe this indicates possible O2 sensor, exhaust leak, or cat Convertor problems. Runs fine at high speeds. Any knowledge on this?

[Trooper2]

Jim, the easiest way that I know of to check the cats for proper function is to read the temperature at the cats inlet and outlet, the temp should be around 100 degrees hotter at the outlet if they are working properly (infared temp guns work great for this). There are 2 reasons why cats stop working; plugging or contamination. If the root cause of the cat failure isn't addressed then new cats will fail prematurely.

Here is a good article that discusses cat failure, what to look for and what else it could be.

http://autos.yahoo.com/maintain/repai

[jimbeaux]

Trooper2 said:

Jim, the easiest way that I know of to check the cats for proper function is to read the temperature at the cats inlet and outlet, the temp should be around 100 degrees hotter at the outlet if they are working properly (infared temp guns work great for this). There are 2 reasons why cats stop working; plugging or contamination. If the root cause of the cat failure isn't addressed then new cats will fail prematurely.

Here is a good article that discusses cat failure, what to look for and what else it could be.

http://autos.yahoo.com/maintain/repai

I appreciate this; thanks!