Hi,
The idea that it has a rough idle is making me think it is something related to the throttle position sensor. When the engine starts shaking with the A/C on, at what RPM does the engine idle? It should be approximately 700 RPMs at idle in park or neutral. Is that where your vehicle idles?
The PCM is what controls the engine idle speed. Different components place a load on the engine. As a result, the PCM adjusts idle speed to compensate for the added load. However, before we jump to conclusions, let's make sure there are no engine vacuum leaks. Here is a link that explains how to check and repair. Do this and let me know if you find any leaks. A vacuum leak can certainly cause a rough idle.
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
Let me know what you find.
Joe
Aug 4, 2023 at 8:32 PM