Here's how to clean the idle air control valve, throttle body and PCV valve on a 4 cylinder Honda Accord, Acura TSX, Honda CR-V or Element.
A dirty idle air control valve (IACV), throttle body or PCV valve can cause rough idle, idle that is too low or high, dull throttle response or a car that doesn't want to stay started once cranked.
Carbon deposits build up on the butterfly valve and IACV solenoid, causing them to stick and function improperly. Sometimes this may result in a check engine light, P0505, P0506, or P0507.
While often the solution is to replace these components, it can get quite costly and cleaning them can prolong their life and be more cost effective.
On most vehicles, throttle body removal is required to access the IACV. The airbox and its accompanying hoses must first be removed, followed by the throttle cable and two coolant lines. Four 12mm bolts and nuts hold the throttle onto the intake, upon which the IACV can then be removed via two philips screws. Sometimes these screws strip out or are hard to get to on the vehicle and you'll have to use a vise grip to turn them out.
Once everything is apart, use carb cleaner, a rag and toothbrush to clean everything out, and put it back in the order it came apart. Make sure all gasket surfaces are clean, and change the air filter while you're at it. Cleaning the mass airflow sensor with electrical contact cleaner is a good idea, if it isn't seized in the air intake.
The PCV valve is on the passenger side of the car, above the alternator. Once the hose is removed, a 17mm deep socket can be used to unscrew it from the engine block. If it rattles when shook, its working fine, but if the ball pin is stuck it won't rattle and should be cleaned and/or replaced.
Once everything is back together, pull the battery terminal to reset the ECU to relearn idle. Top off the coolant and allow the system to bleed out all the air by leaving the radiator cap loose.