P0507 Code: Idle Air Control System RPM Higher Than Expected

🟠 Moderate severity · drivable

Drivable, but the engine idles too fast, which wastes fuel and can feel like the car wants to creep forward.

What P0507 means

The engine is idling faster than the computer expects. Usually this means too much air is getting into the engine at idle — often from a vacuum leak.

How the system works

The engine computer aims for a target idle speed, usually somewhere between 600 and 900 rpm once warm. It controls idle by adjusting how much air gets past the closed throttle: older engines use a separate idle air control (IAC) valve, and newer ones move the electronic throttle plate itself.

P0507 sets when the actual idle stays well above the target, commonly by about 200 rpm or more, even though the computer has already closed the idle control as far as it can. That means air is getting in from somewhere the computer does not control.

Symptoms

Check engine light is on
High idle speed
Engine feels like it's surging
Car creeps forward at stops

Common causes

most common: Vacuum leak
common: Faulty idle air control (IAC) valve
common: Dirty or sticking throttle body
less common: Leaking PCV valve or hose

How to diagnose P0507

Confirm the idle speed. Warm the engine fully and compare actual and desired idle speed on a scan tool, with the air conditioning off.
Look at fuel trims. Positive fuel trims at idle that return toward normal at higher engine speed are a strong sign of a vacuum leak.
Check for vacuum leaks. Inspect the intake boot, PCV hoses, brake booster hose and intake manifold gaskets. A smoke test finds leaks that cannot be seen or heard.
Inspect and clean the throttle body. Carbon can hold the throttle plate slightly open, and a sticking IAC valve can stay open. Clean both with throttle body cleaner. On electronic throttle bodies, do not force the plate by hand.
Check the throttle stop and cable. On cable-operated throttles, make sure the cable has some slack and the throttle returns fully to its stop. A floor mat pressing on the pedal has caused this code.
Perform an idle relearn. After cleaning the throttle body or disconnecting the battery, many vehicles need an idle relearn procedure before the idle settles. Follow the procedure for your make.

How to fix it

Fix	DIY?	Typical cost
Find and repair vacuum leaks	Yes	$10–100
Clean the throttle body and idle air control valve	Yes	$10–40
Replace a faulty idle air control valve	Yes	$50–200
Replace a leaking PCV valve	Yes	$10–40

Common misdiagnoses

Replacing the IAC valve on a vehicle with an electronic throttle, which has no separate IAC valve.
Skipping the idle relearn after cleaning the throttle body. A cleaned throttle passes more air, and the idle can stay high until the computer relearns.
Adjusting the throttle stop screw. It is set at the factory, and moving it hides the real fault.

P0507 vs similar codes

P0506: P0506 is the opposite: idle speed lower than expected, usually a restriction or a sticking idle control.
P0505: P0505 is a general idle control system fault, without saying whether the idle is high or low.
P0171: P0171 reports a lean mixture. It often appears with P0507 because a vacuum leak causes both.