If you are sure the plugs are OK, (I would replace anyway), then
off & a good CAREFUL clean, pay attention to the sealing ring too. There are lots of threads which describe this. Whilst yer in there, check integrity of wiring, connectors, fuse box under the battery,
plugs for damp / corrosion. Get the diagnostics read, but do have an expert interpret the results. For instance Lambda / O2 sensor WILL show, but it's only doing that coz It's too rich.
Originally Posted by Pjg68
Engine is a little juddery, but will not rev much above 4000rpm. Any ideas.
One other thing if you leave it idling it stinks like rotten eggs just before it stalls.
This suggests to me sticky TB.
My faultfinding tip "do the cheapest, easiest things first"
Other "experts" will be along soon.