I just acquired a 2004 S-type which was meant to be a replacement for my 2006 XJ8 with a blown engine. The previous owner said that the catalytic converters had just been replaced, and my son test drove it and said that it was fine. But when I took possession of it the next night, I found that it was misfiring badly. I had to drive it 350 miles in that condition to get to where I could have it looked at. It drove, but lacked power. Also there was a shimmy that developed near the end of that trip.
I took it to a mechanic, the only one I could find in my area who said he could work on a Jaguar. He said that the catalytic converters were melted, fouled, or something and would have to be replaced again before he could work on the ignition systems--coils and spark plugs. Also apparently someone took away at least one oxygen sensor and filled in the hole. He has yet to get back to me with a price for the converters.
I have spoken to some friends who are mechanically inclined and they said that replacing the converters before working on the ignition didn't make sense. So who is correct?
I will also need a new battery and tires, but don't want to expense that if the car cannot be put into driveable condition.

 

Driving these cars with an obvious ignition fault will cause this type of damage to the cats.
Hind sight is a wonderfull thing but it would have worked out cheaper to get it brought the 350 miles on a transporter!

I am amazed that you had no warning lights on the dashboard!

Anyway.
The first thing to do is to read the fault codes that will be stored on the system.

Sadly, but realistically unless it is an STR the cost of replacement cats may well be more than the car is worth!

 

Thanks, that's what I needed to know.
I should have known better but i was stuck in a strange city on a Saturday night with no hotel accommodations and not even a change of clothes. And yes, the dashboard was lit up like a Christmas tree, but nothing I could act on at the moment.
The body and interior are in great shape so if I can get it running I will recoup my investment.

 

You never gave an update, what the issue was... - even before you mentioned the missing oxygen sensor, my bet would have been on a faulty oxygen sensor...: The engine is controlled by a computer, and if that computer gets rubbish inputs (due to broken or missing oxygen sensor (or knock-sensor)), the output from the computer to the engine is rubbish, too - misfire, stall and extreme fuel consumption are indicators...

 

Thanks.
I'm still being put off by the mechanic.

 

Sounds like you need a new "mechanic"....

 

I had a o2 sensor fault and a couple of in and out of limp mode moment's. Car had been off the road 4.5 years. Filled it with 98 and drove 120km round trip.. All good now

 

The reason you replace the catalytic converter‘s before everything else is because it will set codes for the catalytic converter‘s and you might not get the right fuel trim from a straight pipe in there. Clogged cats will mess up any diagnostics. You might stay in open loop. so I would agree replace the cats put new oxygen sensors in. find out what your baseline fuel trims are start fixing vacuum leaks and don’t drive it on the freeway until it’s fixed

 

Warning! Replacing cats but running the car with a misfire can damage your new and expensive cats. So make sure you have fixed it before you drive it far. As mentioned above, replace the O2 sensors at the same time is a sensible precaution.

 

true! I guess it all depends on how bad it is. First things first. Check how bad things are