My 90 XJ-S V12 is nice and smooth LacedMy 90 XJ-S V12 is nice and smooth when cold and pulls well. When warm it when cold and pulls well. When warm it doesn't idle as well, does not pull quite as doesn't idle as well, does not pull quite as strong and gets harsh from 3000 rpm. I strong and gets harsh ftom 3000 rpm. I do not want to change parts willi nilli. do not want to change parts willi nilli. What are the best way of diagnosing for What are the best way of diagnosing for an owner without the really dpecialised an owner without the really dpecialised tools? I replaced coils, rotor, cap, plugs tools? I replaced coils, rotor, cap, plugs and plug leads a couple of years ago. The and plug leads a couple of years ago. The O2 sensors are original. O2 sensors are original. From the above my money is on From the above my money is on overfuelling? Would that have such an overfuelling? Would that have such an effect? How do I diagnose this with effect? How do I diagnose this with simple tools? simple tools?

 

It could be over fueling. Look inside the tailpipes, is there a lot of black soot?
I would suggest changing the O2 sensors, as they should be changed by now. I'd also change the spark plugs again.

 

i would suggest a crash course on iphone keyboarding.

and i would suggest changing o2 sensors. ive got an original set for sale.

 

M90, I think he's using a translator program to convert to English.

 

AAH, ok.

 

Thanks gents. I'll start with the O2 sensors. I didn't proof read when I had posted I have no explanation (good, bad or foolish) for the doubling up. BTW, no iPhone or translator used.

 

you can go back and edit the post for clarity.

the edit button is in the lower RH corner.