Hi I have a minor problem with my 1.8 Freelander. One of the tappets appears to be sticking and causing a slight mis-fire on tick over. Have checked plugs,leads,comp test.Will an engine flush help/cure or is it a head off ? replacement item.It runs fine at normal speeds just slightly rough at tickover

An unofficial trick of the trade is to change the engine oil for ATF, drive the car gently for 20-30 miles, leave over night, repeat gentle drive, drain and replace with engine oil. ATF has very strong detergents and will usually unstick lifters. Obviously you're risking desludging the engine which can cause problems of its own (sludge shifting and blocking oil ways), ATF is also very thin so you could end up with unacceptably low oil pressure with a heavily worn engine.