A rough idle only – the engine is smooth and pulls strong over 1200 rpm or so – is often a vacuum or air leak. If the engine has a rough idle and misses at wot check for good spark. There may be a problem with the cap/rotor. The plugs and wires s/b checked, too. I had a car with a very poor idle and miss and it would come and go. The insulation on one of the spark plug wires was bad and the spark was jumping to the dipstick tube! As a quick fix I put a piece of fuel line between the wire and dipstick and the engine ran smooth again.