Only works when the hood is slammed down and then stops a few minutes later.
its a '91 coupe in pearl white very rare

You have an Infiniti M30? l want one and they are really hard to find. :(

Nope. try to find a infiniti forum

If it temporarily fixes it when the hood is slammed u might inspect the wires around the distributor. l believe the tach signal comes from one of the wires doing to it as the cam angle sensor is within the distributor. I'd check to make sure they're tight & if so, u might even pull them apart & check for corrosion & clean the contacts if there is.

If that is not the issue then u may have to inspect the wiring going to the tach itself & possibly, if the tach is just toast, try out a new gauge cluster. I'd say its more likely a wiring issue as I've rarely heard of Nissan analog gauges dieing. If u do end up replacing the cluster, be sure to get the correct one. 90 models used a cable driven speedometer & the 91-92 used an electric. The easiest way to tell is on the 90 is the fuel gauge was on the left & temp gauge on the right as well as having plain looking text/numbers. The fuel & temp gauges in the 91-92 is were on opposite sides (fuel on right, temp on left) & had a more ''elegant'' looking text/numbers.