if it isnt wiring, it will be most likely the FITV (Fast Idle Thermal Valve) Does the fluctuation go away after the car reaches operating temps?

 

i dont believe so

 

yes i have a 1992 civic dx hatch back. im also using the 1995 b18b p75 ecu.

 

is brake cleaner and carb/choke cleaner the same???? can i use the carb/choke cleaner???

 

try this dude, this worked on my car and i was having the SAMe exact problem...

Unplug that one piece from your iacv, not the 2 hoses that other thing. Thats gona throw a cel, but dont worry its ok. This should set your idle at a certain position. It has to do with your idle regardless of your engine's temp, so even if its cold or hot its gona idle at whatever you set it at. Your car will probably actually run most smooth and quicker response too, it helped mine ALOT. All you do at that point is adjust the screw on your fitv or whatever its called, and turn it down to what you want, prefrebaly about 900-1000 for my likings. Anyway, if that doenst fix it, then you got a leak or a bad iacv, so ya. Try this
-Mike

 

I did exactly what you said and cleaned the IAVC. Now the idle doesn't bounce from 800 to 1500, but sits at 1200. Do I need to adjust the bolt that adjust the idle now????? Thanks

 

how do i check the fitv screw????? and what does it do??? i cleaned the iacv and now it doesnt bounce from 800-1500, but sits at 1200. how do i adjust the idle to the stock setting of 875-900??? Thanks

 

You can check if the FITV has backed up by taking off the intake hosing from the throttle body. Inside the throttle body is 2 holes. One leads to the IACV, the other to the FITV. I believe the FITV is the bottom hole in most cases. When the car is at operating temp, the FITV will shut off and the IACV takes over. You can check this by plugging the bottom hole with your finger. If there is still vaccuum at operating temp, your FITV plunger has backed out causing the high or fluctuating idle.

What the FITV does is it has coolant lines that run through it. When it is cold, the FITV plunger backs up letting more vaccuum in causing the motor to idle higher to allow it to "warm up" ...when the coolant is at operating temp, the plunger of the FITV (made of some kind of wax) slowly closes up b/c the wax is softened. This causes it to close the FITV and allow the motor to idle at lower RPM.


Did you by any chance mess with the idle screw? If so, that is your problem. If you havent, then it is most likely the FITV.

 

havent touched the idle screw.

 

is that how i adjust the idle???