Hey guys,

I had a O2 heater relay fault on my 2006 XJR front fuse panel. I just installed a second hand part (same part number as original), after replacing the fuse box the car will not run properly, it starts with high revs then drops down and the revs pulse up and down, then drops until it wants to cut out. If I give it gas it's rough. I put the original fuse box back on and I still get the same issue. Oh, the engine light went off for the O2 relay after I put the new fuse box on. Seems I solved one problem just to create another.

Any help would be appreciated, as my cat is wounded in my drive way.
Thanks...

 

You will need to start with SDD and examine DTC's and use the Diagnostics to help you narrow your issue.

 

Thanks for your input BOX, I'm not a mechanic so I don't have DSS or a compatible OBDII scanner. The donor car was a 2008 XJ8, but the part number was the same as mine, so I assumed it would be the correct part, as the parts supplier listed their part as compatible with my 2006 XJR.

 

If the part number is the same I would think you should be good.

However if you ever use the "compatible vehicles" icon on Ebay never trust that unless its a large experienced Jag parts seller.

A careless seller will allow Ebay to automatically generate the "compatible vehicles" listing especially if they choose an item thats listed and choose to sell a similar item.

 

Ok, I decided to leave the Cat overnight and I tried it this morning. I started it up and drove it straight away and didn't give it a chance to idle and splutter. It was rough for the first few miles, but then it came good.

I don't know, maybe the issue was due to the ECM trying to compensate for the previous faulty fuse box, once the new fuse box had been installed it needed some miles to adjust to the new change.

 

Not the faulty fuse box, but revising all the settings from those it had 'learned' from its previous engine to those needed for yours.