Mick, a non cost diagnosis- do you have a throttle position sensor on the side of the plenum, something like this?
https://www.ebay.co.uk/itm/12490420...r=&widget_ver=artemis&media=COPYTry unplugging it and go for a run. You won't get the oomph out of the ecu, but everything will run at default settings. If the symptoms stop, this could be the part to replace. Mine went brittle and haywire after 20 yrs service; it buggers up other settings in the ecu, intermittently, when it begins to fail. Don't 'be tempted to replace with a chinese copy, pay the LR tax, it saves mis-diagnosis. I suspected my TPS, replaced with a copy, and had symptoms return. My mechanic son suggested unplugging the TPS, hey presto, dodgy copy and faulty part diagnosed. Lo cost to that point !!, but trouble free motoring now.
Good luck with finding the cause
Phil
