timewarrior2001

Sorry if this is in the wrong place, couldnt think of a better place for it.

I have a T reg Vectra 1.8 16v LS

Recently its been running a little odd, I can drive 40 or 50 miles down a motorway, but when I come off the motorway to a junction the engine will cut out instead of idling.

Now the engine has the ability to automatically adjust the timing if i use super unleaded or normal unleaded fuel, however this has not made any difference. I've tried cleaning with redex, no difference.
Its really bugging me and is now getting dangerous as it cut out in the middle of a roundabout yesterday. The spark plugs are less then 12 months old.

Does anyone have ANY ideas?
Or can give me directions to a decent garage in teesside that can run engine diagnostics