1992 Nissan D21 150k miles manual and it does not have obd2 system my vehicle first started with a rough idle almost sounded like it had a misfire of aftermarket camshaft then it progressed to a worse idle and am not at the point where it’ll start and idle terribly for a couple seconds and shut off it also run closer to normal with the mass airflow sensor unplugged and I’ve changed plugs wires distributor cap and rotor fuel filter pcv valve and still no solution
Make sure your wires from the distributor cap to the plugs are in the correct firing order. If they are, check for vacuum leaks. Good luck.
You might want to do a compression test to check internal engine condition. Vacuum leaks are a definite possibility on a 32-year-old vehicle so you'll want to test for those. Clean the MAF sensor and throttle body. You could also try checking for any OBD1 codes that may be present.
