Hey all my 1994 Jaguar xjs 4.0 has developed a nasty shake at rpms below 1500 and I’d like to have some idea of what’s wrong before I take it in any advice would be much appreciated

 

Perhaps start by checking the integrity of the connections on each spark plug lead. Also check that the spark plug recesses have not got puddles of oil at the bottom which causes the spark to break down and will be more noticeable at idle.

Good luck

Paul

 

This becomes very obvious in the dark too. You can see the spark jumping to the engine block.

 

I just solved a "shake, bad idle" issue on my 93. Turned out to be a bad idle speed motor combined with hard to find air leaks.

Good luck!
Dave in AZ