rough idle

[Repteel]

my friend has a 93 civ hb, d15b7 motor, idles at 1800 rpm for 30 seconds, the drops down to 450 and then yoyos back and forth. after driving the car for about a minute the engine light comes on and sets code 43, car is buring super rich, we removed the IAC valve and cleaned it with brake clean, the IAC doesn't make any noise when you shake it, cleaned the throttle body, swapped the TP sensor and the HO2 sensor from a good working engine, anybody got any ideas????

[AudioGuy93DelSol]

Try running some fuel system cleaner through it. See if that clears it up.

[Repteel]

already put combustion chamber/ injector cleaner with last gas of tank, would the fast idle screw make it yoyo up and down??

[AudioGuy93DelSol]

Yeah. Check this out.

[jclark]

A vacuum leak will do the same thing.
Check all your hoses and intake connections very carefully.

[Schister66]

Originally Posted by jclark

A vacuum leak will do the same thing.
Check all your hoses and intake connections very carefully.

x 2

[Repteel]

well your both right, the FITV housing is cracked, so it's causing a vaccum leak, we've put silicone on the crack as a temp fix, seems to be working ok, now we're looking for another housing or FITV, thanx for all the help