i have an 89 crx with a obd0 b16
after the car warms up if the rpm's get below 3k the check engine light comes on
if i turn the car off and then cut it back on the light goes out but always comes back on. while the car is running the ecu shows: two long flashes in a row followed by 3 short flashes in a row. i replaced the map sensor but it still does the same thing.

 

well it says code 23 is your knock sensor....i hope this will help ya: https://honda-tech.com/zerothread?id=468260