Honda Car Forum

My 94 civic has a 1.5 l pulsates up and down from 1000 up to 2500 rpm?

is it showing any warning light,s............check your map sensor.....then check for any vacuum leak,s.

That's called "hunting for idle".I've found it to be a throttle position sensor or a vacuum leak.

sounds like your low on coolant,believe it or not,when the coolant is low the coolant sensor and idle controll motor rely on coolant to get accurate readings to the ecu,if the cool is OK then you could probably need an idle con troll motor(iac) or your getting air into cooling system,possible head gasket,good luck

you have whats called an idle air control valve take the 2 screws off then pull the top off the iac then you look down inside the iac assembly see that screw down there? tighten up that screw then put your iac back together get a new iac gasket before you start this job also disconnect the negative battery cable before starting also for the first 10 miles drive as you normally would but understand the computer has to go through whats known as an idle relearn procedure. also change your air filter.if dirty.

Idle Air Control Valve (IACV) is bad or clogged.

what Roger N said