Land Rover Repair: intermitant irregular running, silicone plugs, vacuum leak

Question
Dear john i have a 2.5L petrol 90 1986 112000 genuine mls that starts 1st time and drives ok for about 3 miles,then it runs erratic and wont tick over without keeping my foot on the gas.After restarting several times which again it does 1st time and giving a bit of gas it then runs normal and the problem does not reoccur until the next day when starting from cold.Ht leads are brand new[silicone]plugs points timing etc are ok although vacuum to distributor doesnt seem very strong?.I have limited  mechanical skills but i do service the vehicle regular and have not had a problem in the two years ive had it.Thankyou for your time karen  

Answer
Hi Karen,

nice 90 and low mileage too!  Sounds like it could be ignition timing, possible vacuum leak, even fuel pump.

It seems to start well, warms up (3 mile drive) then misbehaves.  When did you last change your plugs?  Have the cylinder pressure tested - can reveal internal problems.  Could it be the timing belt?

This is one of those awful problems that can't be pin pointed by a single component.  You'll need a diagnostic analysis to help track down this problem.

Best of luck,

JohnMc