Hi shaun,Raz could be right in his diagnosis,these intermittent faults can be very difficult to sort out and just guessing as to what the problem is can end up costing a fortune,think the temp sensor is at the back of the head and when removed must be replaced with a new one and has a torque setting,think it is 4NM,this acts on the exhaust valve on no.4 cyl and may be a bit awkward where it is near the bulkhead,dont think these are that expensive and other things to check are egr valves,was at another garage today and they were on about a transit with bad running and intermittent smoking but this was a fwd and said they got an aerosol of egr/inlet system cleaner,think Holtz supplied it,get it up to working temp.keep the revs at 2k and spray 1/2 the can into air inlet hose,keep revving for 5 mins then empty the whole can and this cleaned out the whole inlet system and said they have had no problems since,these are cheap fixes and wont cost a fortune and are worth a look,good luck
cdc
February 2011