x-type 3.0 litre lpg

[warrior1872]

My x-type wont rev above 3000 rpm on gas and it doesnt run normal on petrol it has a lumpy idle has anybody got any ideas ive been told it could be the valve seats

[rossko]

Could be, amongst many other things. What, if any, diagnostic access do you have e.g. OBD reader?

[xj8user]

Could also be a vacuum leak or as rossko said many other things?
you need to pull some codes or data!!

I am working through a similar problem on an XJ6 with same engine, there are specific areas which have known vacuum leaks which can cause rough idle, as well as duff plugs, coils etc?

I hope it isnt VSR as that is expensive to sort!! try the cheap options first.

Joe