The IAC valve regulates the idle speed by controlling the amount of air bypassing the throttle plate. When the AC compressor kicks on, it puts an additional load on the engine. A functioning IAC valve compensates for this load by increasing the idle speed to prevent stalling. Since your idle drops and only returns to normal after you turn off the engine, the IAC valve is the prime suspect. It's likely sticking, dirty, or failing to open sufficiently when the AC is engaged.
Here's what you should consider:
* Clean the IAC valve: This is the first and cheapest thing to try. You'll need to locate the IAC valve (consult your repair manual for its location), remove it, and carefully clean it with carburetor cleaner or a dedicated electronic parts cleaner. Make sure to let it dry completely before reinstalling.
* Check the IAC valve wiring and connector: Ensure there's no corrosion, broken wires, or loose connections in the IAC valve's wiring harness and connector. A faulty connection could prevent the valve from receiving the correct signal.
* Inspect the throttle body: While you're working in that area, inspect the throttle body for buildup of carbon deposits. A dirty throttle body can also contribute to idle problems. Clean it thoroughly if necessary.
* Check the AC compressor clutch: Although less likely, a faulty AC compressor clutch that draws excessive current could also cause the idle drop. This would require more specialized diagnostic tools to determine.
* Replace the IAC valve: If cleaning doesn't solve the problem, the valve may be faulty and need replacement. This is a relatively inexpensive part.
Before you start any work:
* Consult a repair manual: A factory service manual or a Haynes/Chilton manual specific to your 1995 Suzuki Sidekick will provide detailed instructions, diagrams, and torque specifications. This is crucial for working on your vehicle safely and effectively.
* Disconnect the negative battery terminal: Always disconnect the negative battery terminal before working on any electrical components to prevent accidental shorts or damage.
If you're not comfortable working on your car yourself, it's best to take it to a qualified mechanic for diagnosis and repair. Ignoring this problem could lead to further engine damage.
