i have a 1992 civic and the idle keeps going up and down rapidly. I changed the throttle body cause it has the built in sensors on it for the 1.6 but that didnt help. i cleaned out the body with carb cleaner and blew it out after. still no luck. i read that the coolant could be low and cause that but i dont think thats it. any suggestions?

 

Did you remove and clean the IACV mounted on the back of the manifold near the throttle body? Also humor us and actually check the coolant level. With engine COLD, take the radiator cap off and look in the radiator itself. It should be full to the top.

 

In addition to what mk378 mentioned, clean and adjust the FITV and bleed the cooling system. Any CEL codes?

 

okay ill try those suggestions. but it idles from about 1500 to 2000 up and down like every sec . so wouldnt it happen slower if it was a valve?

 

That high is probably a leak somewhere. Make sure the throttle cable goes slack and plate closes fully. Take off the intake pipe from the air filter and notice that there are 3 holes in the side of the throttle body before the throttle plate. Start engine and see which ones are drawing air. Only the top one should be when idling too fast. The bottom one goes to the FITV and the back one to the IACV. The FITV should be closed except when the engine is very cold (below 60 F).

 

i found the problem. the intake gasket has a leak and it was causing the IAC to go crazy to try and compensate for the the air getting sucked in threw the leaky intake gasket.
but thank you everyone who gave me suggestions.