you can get a voltmeter that plugs into the lighter socket to check your alternator but don't think thats the issue. i would suspect your distributor or coil or the ignitor. could also be a loose/bad connection in one of the power boxes, if its not missing at idle try wiggling and moving all the wires you can reach under hood and dash and wiggle the fuses and see if you can get it to miss. intermitents can be a real pain