I have a 2003 xj6 3 litre, when driving from cold at mid revs I can see the revs counter fluctuating a couple hundred revs and I can feel the car holding back as if it's mis-firing but no noise.

As it warms up the issue lessons and eventually goes all together. it does this every day, no fault codes showing.

can anyone help?

thanks

 

Is this when cruising at a steady speed, if so it sounds like the gearbox torque converter. Cured by gearbox oil change and reflash or (as mine did) a replacement torque convertor.

 

Thanks for the reply. No its at low revs around 2000 rpm or below. acceleration seems fine

 

You have the notorious 'hunting' syndrome. My car has had it from when I bought it in 2010, and still has it despite attempts to cure it. As you say it eventually disappears, and this when the transmission fluid has warmed up. I just put the transmission into '3' for a bit. As far as I can tell no harm is caused, and as my car had it at 30k miles on purchase and still has it now I'm on 114k miles that seems right. Later cars had a different torque converter clutch which apparently gets rid of it; expensive fix though. I was told the TCM engages/disengages the lock-up clutch to warm up the transmission fluid, so it is a software issue. Later torque converters have reprofiled friction surfaces.

If only one could get hold of the TCM source code to fix it !!

 

Thanks for that I will give it a try.

 

Yes it sounds like the problem mine had.

 

Any further suggestions would be greatly appreciated thanks

 

As mentioned earlier, gearbox oil change and gearbox module reflash.