i would be willing to bet that this is a crank sensor i had the exact same problem on a VW. unfortunately there is no real way to be sure besides attaching a oscilloscope to the sensor and drive around tell you have the problem again. some times you can get away with cleaning the sensor they get a build up of old oil on them making the reading unreliable. but i would suggest you just bite the bullet and replace it.
I have a 97 Cougar 8cyl. On 4 occasions having parked the car and turned off the motor, I have been unable to start it again. This is over a couple of months .The battery turns the engine over but it refused to fire. On one occasion I had it towed back to the house where it started without any trouble. On the other occasions I left it up to 2 hours whereupon it started again. I am told by mechanics that I need to have it tested when it is in the failed mode, but there appears to be no way I can induce it to fail on demand. It has been suggested that the crankshaft sensor may be the problem but how can I be sure.?
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