alright,if you think its that cylinder then start the car,while its running pull the plug off the injector for that cylinder and if the car stays idiling the same then it is that cylinder.if it does change its idle then you have to figure if its spark or fuel.if you checked the spark then check the wiring to the injector,the plug itself.unplug the injector,hook a test light up to the plug when the cars idiling.if its coming on when that cylinders supossed to be fireing then the wireing is good.you have to hook it up to the power wire,usally green with black stripe.check the injector itself by hooking a power wire and a ground wire up to the tabs were the plug would go.just run 2 little wires from the battery.just tap them on the injector.if its clicking or popping then its fireing.it also cleans the injector.also check all the engine grounds.if the motors shaking real bad then mabye some mounts would help.good luck.