The 2 sensors for the ignition spark are the crank sensor and the pickup sensor in the distributor. Since you know your losing spark and the crank sensor is good then its easy from here. Check to make sure you have power on the coil the next time it happens. If you have power on the coil and no spark then its after the coil and before the plugs in your ignition system. The pickup sensor in the distibutor, coil, or the distributor itself.