Strange rattle sound only at a certain RPM

[kkash48]

Thanks!!

 

[GNVenom]

I had an 86 GN with the early design crank sensor, that did the same thing. Turned out one of the square keys that position the sensor to the bracket slipped out, causing the sensor itself to rattle loudly at certain RPM's. Replaced it with the new style designed sensor, problem solved.

 

[turbofabricator]

Another common source of a rattle is the steering column lock out rod rattling against the drivers side header
In gear it comes real close to the #5 header tube. Years ago I fought and fought this issue. I ended up using a light throttle return spring going from the lock out rod to a small hole I drilled in the inner fender at the lower edge.
To verify, put your car in drive with the ebrake on and working.(or have a trusted friend in the drivers seat applying the brakes) and look at how close the rod is to #5 header tube.