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Q: Rumbling on acceleration and idle while using air conditioning.

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When accelerating it feels as if the car rumbles and is sluggish to gain speed. Also when turning it's even more noticeable. After 3k rpm the rumbling is non existent. Happens a lot worse when the AC is on.. and while AC is on the rumble and sputtering happens even while idling.

When stopping and then accelerating even when AC is off it will rumble for just a brief moment before smoothing out.

Question is.. what could it be? Someone mentioned to me possible IACV. Or even the compressor. Maybe a cylinder compression test is needed? Any advice would be appreciated.

My car has 165000 miles.
My car has an automatic transmission.

A: This may be related to a dirty or failing i...

This may be related to a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle's computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature, and electrical system load or voltage.

When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. This is all controlled by the idle air control valve. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this may indicate a dirty or faulty idle air control valve. In cases where this valve is dirty or failing, your vehicle may stall instead of slowing to an idle after the release of the throttle. This may be the cause of the symptoms you are experiencing.

I would recommend having an expert mechanic, such as from YourMechanic, come to your location to diagnose the rumbling and replace your idle air control valve if needed.

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