I have an 3.0 2002 s type that is throwing engine codes p0430 and p0420 as well as a misfire on cylinder #6. I had a vacuum leak for a long time, but has since been fixed. The car runs rough. About two weeks ago, the drivers side cat got so hot that it was glowing red. I let it cool off and it didn't overheat the cat again after restarting the car. However, the car continues to run rough. When driving down the road yesterday, the car was missing badly and the check engine light would blink when i was coasting/leveling out. I know I need new cats. Are the magnaflow universal cats ok? I found this one, Part # 99204HM. But the muffler shop that I spoke to said that the jaguar needs a 3-stage cat and the magnaflow cats are 2-stage and that it wouldn't fix the problem. Is that true, or is the magnaflow universal cat ok?

 

Before you screw around with the cats get the car fixed! You have big problems if the check engine light is flashing. That's telling you that you are operating in the danger zone.

You have the V-6 which has list of known problems. Search on here to get the list. At this time I would replace all the coils and plugs as well. You have more than one problem but they are not that hard to fix properly. Some great how to's on this site!

After the car is running properly with NO check engine lights then fix your cat problem.
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Flashing MIL = cat-damaging misfires. As above, you need to fix the cause and yes they've been covered here a lot, with fixes. Do some reading

 

Just over from the X-Type list with a newly purchase 4.2l...

Catalytic converters are a real horror for X-Type owners. They are part of the exhaust manifold and are very difficult and really expensive to replace. So I'm curious about them on V8 S-Types. Are they positioned under the car and relatively easily accessible or are the pushed forward towards the engine and blocked from under the car?
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Jaguar: Grace, Pace, and Space - Sir William Lyons

 

S Type cats and O2 sensors are pretty much out in the open. Not as tight as the X-Type. You can use aftermarket cats with no problem but it will require an exhaust shop to install them.
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A Big +1 to tbird6 and JagV8 - you need to get the coils changed out ASAP and also check through the other "known" causes linked to the V6 motor... like the intake O-Rings, etc...

 

I changed out the could and it runs much better. cel is off. I'm going to change out the o2 sensors as a precautionary measure and see if there are any recurring issues. thanks to everyone for the help.

 

could = coil with auto correct on phone