I'm new to the world of mechanics, and don't really know much, but I've decided to start working on my 91 honda accord ex coupe. I've been successful at clearing all the CEL codes, but I still have a rough idle problem. I've cleaned the IACV, the FITV, and the inside of the throttle opening, and tightened the FITV, but still has a rough idle. There is one hose just above the throttle opening, (I can't post a picture, but hopefully you know the one I'm talking about. It seems the hose is usually a braided red hose.), that isn't connected to anything, where does this hose go? Also I've noticed that some cars have a sensor on top of the intake, should mine have this too?

 

If I remember correctly that red braided hose usually goes to the manifold absolute pressure (MAP) sensor located in the black box mounted to the firewall.

If that hose is not connected to anything it will cause an idle issue for sure. It is basically a vacuum leak and will cause an erratic idle. If if is the MAP sensor hose and the MAP is not connected to vacuum. It will cause even more issues with engine operation.

 

the red braided hose is the evap hose it goes to the cannister