The symptoms are consistent with deposits in the throttle body. There are other potential causes. These deposits accrue in the intake manifold over time. They build faster with short trips and low quality fuels. Inspection and cleaning of the throttle body would be first thing to look at for this symptom. This engine is equipped with a computer controlled throttle system. It is designed to adjust its opening to keep the idle speed close to 700 rpm regardless of engine load. If to much dirt collects around the throttle blade the system can get beyond the limits of the systems ability to adjust idle speed with the extra load of the air conditioning.
To clean the throttle use a soft cleaning cloth soaked in a solvent. Open the throttle blade carefully. Clean the throttle blade and the surrounding bore. Do not scrub, let the solvent do the work, no scratches are allowed on the polished bore.
After cleaning start the engine and let it idle for at least 20 minutes while the system learns it's new throttle position. This vehicle should relearn on its own. It may need to be revved up and put in gear several times during the learing time. Note that other designs require tools and procedures to perform the throttle system relearn.
- These geared blades are very strong and can damage body parts if they activate during cleaning, Make sure the vehicle key is away from the vehicle. Open them slowly and carefully. We use shotgun bore cleaning swabs so we do not have to insert fingers into the blade area
- Do not spray solvents into the bore and intake, just soak the cloth.
- Do not use metal tools for cleaning, it is easy to cause damage and these units are expensive.
If indicated, have cleaning done by an experienced technician if at all unsure since it is possible to get injured or damage a very expensive part.