Changed pcv valve, o2 sensor, oil plugs, wires, fuel filter, main relay, distributor, Already has new clutch. When making turns, etc. the car stalls when downshifting into a lower gear.If Itake it out of that gear, it runs again and it lets me down shift then. It also happens when coming to a complete stop, sometimes. 1989 honda civic 1.5 L

You need to have your throttle angle checked. It sounds like its shutting down from lack of throttle.

. Set idle to 700 rpm, after it reaches normal operating temperature.

. Check timing with a timing light--it may be retarded too much.