Vibration with compressor on

Hi,

Is there any noise associated from the compressor? Also, I need you to pay attention to the engine RPM's when you feel the vibration. If the RPM's are dropping too low, that will cause what you feel.

In the throttle body is what is called an idle air control valve (IAC). This component is designed to maintain idle speed. When an extra load is placed on the engine such as the AC, the IAC allows the idle speed to increase to compensate for the load. If it isn't working, the RPM's may be dropping too low. This is just a theory at this point.

Let me know.

Joe

Anything is possible. It wouldn't hurt to check the AC system high and low side pressures to see if something is happening there. However, if it has been that long, I would think it isn't and issue. If the RPM's are at 600 with a load on the engine, that is a bit low. It should be closer to 800. Cleaning the throttle body may not be a bad idea. If it idles at 600 with or without the AC running, the IAC seems to be doing its job, but the idle itself seems low.

Here is a link showing how to service the throttle body. Let me know if it helps.

https://www.2carpros.com/articles/throttle-actuator-service

Also, I really question of the idle air control valve (IAC) may not be working as it should. Take a look through this description of its job and what it is responsible for (toward the bottom of the article.

IDLE AIR CONTROL (IAC) VALVE

NOTE: The IAC valve assembly is not adjustable and cannot be cleaned, also some IAC valves are normally open and others are normally closed. Some IAC valves require engine vacuum to operate.

The IAC valve assembly controls the engine idle speed and provides a dashpot function. The IAC valve assembly meters intake air around the throttle plate through a bypass within the IAC valve assembly and throttle body. The PCM determines the desired idle speed or bypass air and signals the IAC valve assembly through a specified duty cycle. The IAC valve responds by positioning the IAC valve to control the amount of bypassed air. The PCM monitors engine RPM and increases or decreases the IAC duty cycle in order to achieve the desired RPM.

The PCM uses the IAC valve assembly to control:
- no touch start
- cold engine fast idle for rapid warm-up
- idle (corrects for engine load)
- stumble or stalling on deceleration (provides a dashpot function)
- over-temperature idle boost

The problem with the IAC on this vehicle, it can't be serviced. By the way, I looked up idle speed and it indicates it should be right around 775 RPM's. Honestly, if it was increased to that point, the vibration wouldn't be as noticeable.

I will watch for your reply. Let me know if any of this helps.

Joe