Jaguar X-Type 2.5 "jerking" on throttle

[bigbob77]

I have a 2001 Jaguar X-Type with the 2.5 petrol engine and a manual gearbox.

It has a very bad "jerk" when I apply or release the throttle. This happens in any gear and at any speed, although it is more noticeable at lower speeds.

As well as this, there seems to be a couple of "flat-spots" in throttle. In neutral, it revs from 800rpm (idle) to 1000rpm no problem... But then it sort of jumps up to 1300rpm. It's not possible to make the revs sit between 1000rpm and 1300rpm. This also happens at other points in the rev range, but not as bad.

I've already tried:
Replaced throttle body (including throttle position sensor)
Replaced throttle pedal (including throttle position sensor)
Full service with all 6 spark plugs replaced

Any ideas?

[maniac0796]

Does it do it through all temperatures? Or only when cold or hot?

[bigbob77]

All temperatures. Starts doing it as soon as I start the car.

But actually that reminds me... every once in a while, like once a week, there will be a period of about 20 seconds where the "jerk" is gone! It seems very random and doesn't seem to be connected to anything like gear or road speed as far as I can tell.

[maniac0796]

Maybe try getting the MAF sensor or coil pack (and HT leads if it's got any) checked out. Those would be my next ports of call.

[veedubmadness]

CHECH ALL VACCUME HOSES 4 LEAKS, GET IT PUT ON DIAGNOSTICS READER SEE IF ANY FAULTS STORED EMWL DOESNT NEED TO BE ON TO RECORED A FAULT.