Just purchaced 90 honda civic with this problem. Has 1.5 sohc and 4 speed. While going through gears will cut out at about same rpm like it is hitting a rev limiter.1 at 10 mph 2nd at 35 3rd at 55 4th at 73 does not have tach maybe at about 3500 rpm also does same when racing engine. Does this consitently when hits rpm. Have changed plugs, wire, rotor timing belt, fuel filter and water pump and still same? It runs great up to this rpm range does not stall or miss. I am at a complete loss. Have not heard of read about problem such as this. Thank you all for any help

Replacing the Ignition Control Module (ICM) and coil should solve the problem. Here's how to do the work yourself:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-46563-4.html#post265896

Your coil setup is different on your 1990 Civic, since you have an external coil. The real culprit is likely the ICM. If you want, most auto part stores will test ICMs for free.