SOunds like you may just have to increase the idle speed a bit. It's not an electrical interlock of any kind. If you want to prove that the neutral safety switch is working right, try starting in "N". If that works fine, then it's adjusted right. Either way, it only affects the starter solenoid circuit.

YOu might want to make sure there's not a broken engine mount or something real obvious like that. The fuel injection harnesses have a ton of wires and don't really like being flexed that much- bad mounts flex the wires. On my 75, there were about 50 wires (it seemed) all going to a common ground point in the engine compartment- cleaning up these ground terminals and the bolt with a fine wire brush will sometimes clear up a running problem.
Good luck.
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Rob Bareiss, New London CT ::: "Roterande Fläkt Och Drivremmar!"