Hi, I am anew member and have a 2002 Jaguar 4ltr S type Sport with 127Km. My wife has a 2004 2ltr X Type.

The 4Ltr S type has a shuddering fault after driving of a while mostly when accelerating up a hill. The plugs and coils have been changed and the torque converter has been removed and serviced. The car runs smooth and has great acceleration but when the speed seems to be over 80Kmh it starts to shudder. The mechanic said he does not know what else to look for. I would be grateful for anyones replies on this issue

 

I'd be looking to blame the transmition , that is if the engine is infact running on all 8 under load , it should throw a code if the engine is missing, but not always . you could use a scanner to watch your fuel trims to confirm that it's not the engine , that should help narrow it down.
Also check your engine and trans mounts.

 

I have the same model 4L Stype year 2000 with 95K miles (152K kilometers) and doing the same thing shuddering when accelerating up the hill around 45 mph (72kph) like its having problems downshifting gears. Have you or your mechanic found a resolution to your issue yet?

 

Bad coil(s) maybe.