Re: missing and idling bad!!?
wouldnt normally visit the 145 lounge but saw your post and it sounded familiar.
first things first tho, the T. Spark engines are anything but sh*t mate. just look after them and they will do you well.
ok, idle problem could be something as simple as a clogged air filter but as you say she runs fine the rest of the time i suspect a clogged throttle body. this is the part at the end of all the black intake pipes. it is common fault for the throttle body to get a build up of oil and grease on it which, when cold, causes an erratic idle. the easiest solution to this is to buy a can of 'carb cleaner' from your local auto supply shop (not very expensive), remove the intake pipe and apply sparingly to the throttle body, give it 5 mins or so to soak in then remove it with a clean cloth. should help smooth out the idle. as for the missfire, normally down to a worn HT lead or spark plug. can sometimes be more sinister but that is where i would look first. rumbling from the rear? is it not the exhaust blowing?
i would recommend a good service is in order, get the spark plugs replaced and the engine flushed. if it doesnt completely cure it, tis never a waste as it helps the engine run better anyway.