I'm sure most of you have had this problem. I have a 91 Accord EX 5 speed, when its in neutral the idle goes up and down. I've been told its the Auto Idle Sensor and the Air Fuel Control Valve, I have no clue what to do, and I dont have the extra money to go replacing everything. Any advice.

 

Mine does the same thing when it's cold. Once it warms up it's fine though. Have you tried cleaning the idle air controller?

 

Normally it's the FITV that needs to be opened on the top of it and the plastic screw thing turned clockwise until it bottoms out. should be a sticky in the faq's section. You can clean out the IACV while your at it.

 

your problem is your fast idle valve. located on the right side of the intake. two screws on top and a cap. take it off. with a flat head screw driver turn it clockwise until its tight. not to tight or youll mess up the wax. just a lil of pressure should get it turning. if you tighten it and it still does it. turn on your car when its cold. open that same cap if you hear air then its a leaking fast idle valve

 

your problem is the idle air control valve (iacv) its a cylinder with black and a two wire connection if front of the intake. unplug it. remove both bolts. remove it carefully. take off the gasket it has with a tiny screw driver. after that get some carb cleaner and blast it. the carb cleaner sit in it for about 5 minutes and dump it. repeat process at least 3 times. leave the valve off. take of the intake tubing. when off look into the throttle body. should be two holes. spray those holes with carb cleaner. clean your throttle plate while your at it. you will feel the difference. put everything back together. and start her up. should have no problem. i would recommend some sea foam if your having problems like that already. with improve throttle response. better gas mileage. cleaner idle. and stronger engine. also you might feel the pedal a lot smoother. i did it to mine. and honest i dont have to press on the pedal so much no more. i feel a 100% lighter car. thats what you will feel.