In the intake manifold plenium, its a 2 wire sensor
no where
The Throttle Position Sensor is located on the throttle body
probably one located just after the engine on the exhaust. by now this sensor will be stuffed
the fan sensor will be located underneath the distributor it should be a 2 wire plug and the sensor itself should be screwed into the head
the fuel filter is located on the firewall
It will be in the ducting before the throtle body.
Under the dashboard in the left compartment
yes
Under the drivers side dash
The 1989 Honda Civic is not equipped with an EGR valve.
a new oxygen sensor might be needed
The spark plug gap for a 1989 Honda Civic LX is .044" (1.11mm).