it was missing,back firing reving itself but not all the time when it was cold it ran fine and when it did play up reeking black smoke and stinks o petrol, what happens is when car heats up it thinks it is still cold so its letting through more petrol and so flooding itself even if it isnt that its worth just trying for £5 u cant go wrong all u need to change it is a 19mm spanner,its at the side of the head on my car but theres 2 ones blue n ones green mines was the blue theres a small clip u need to slide off b4 u can get the wires of the connector, anyway hope that helps, im female so that shows u how easy it was 2 do lol