The check engine light came on and after getting the code (301 or 311)from Auto Zone said that my #2 cylinder is missing. Goes on to say could be plugs, wires, massive air flow sensor, vacuum leak, fuel injector and or sensor. I replaced the plugs and put some fuel injector cleaner in the gas with no change so far. I also noticed the missing is much more pronounced at cold startup, after it warms up it runs smoothly. I don't want to start replacing all theses items, does anyone know how to check sensors or troubleshoot this?