Hi, extract from Canadian Digi site...........seems familiar!
Idle Stabilizer Valve (ISV) Dirt in the Idle Stabilizer Valve (ISV) is a likely cause of erratic idling and stalling, especially when the air conditioner compressor cuts in. A dirty ISV will cause the car to not idle at all, or may cause the idle to lope up and down between 700 and 1500 RPM.
The ISV sits on top of the engine just behind the valve cover and in front of the intake manifold. It is designed to allow a metered amount of air to bypass the throttle valves depending on engine load, temperature etc. to maintain an even idle speed.
To clean the ISV, remove the valve from the engine. Spray the ISV liberally with carburetor cleaner or throttle body cleaner. Use rubber gloves and work outdoors because this cleaner may contain toluene or xylene or both. These chemicals are extremely nasty.
Don't use brake cleaner - it can destroy plastics and rubber. Also, brake cleaner contains perchloroethylene, an even scarier chemical. Definitely try to avoid breathing any of this stuff.
After taking precautions, spray the cleaner into all three openings in the ISV and allow the black gunk inside to drain out. Carefully use a small piece of wood as a scraper to clean up the interior of the valve. Try to get the metal inside as clean as possible. Spray again and repeat until it sparkles inside.
ISVs do fail outright and then you are faced with an relatively expensive fix. At least the part is easy to replace. But before installing a new ISV, always try carefully cleaning the old one first.
A properly working Digifant idle stabilizer is effective enough to allow a manual transmission car to creep along at idle speed without stalling.
