Can a high idle damage my engine?

Not immediately, but a persistent lean condition from a vacuum leak can cause engine knock over time. Address it within a few weeks.

Why does my idle eventually come down but take a long time?

The PCM may be trimming fuel or IAC position to compensate. Once it adapts, the idle can drop, but the root cause of the extra air is still present.

Is P0507 common after replacing the throttle body?

Yes, if you did not perform the idle relearn procedure afterward. The PCM needs to relearn the new throttle body's parameters.

Codes › P0507

P0507: The engine is idling too high

Idle Air Control System RPM Higher Than Expected

Moderate severityCan you keep driving?

Drive to a shop. A high idle is not an immediate breakdown risk but is abnormal and can indicate a vacuum leak that may worsen. Do not ignore an idle above 1,500 RPM at a warm engine.

What it means

P0507 means the engine is idling higher than the computer's target. The engine is getting more air than the IAC system is commanding. The most common cause is a vacuum leak, which lets unmetered air into the intake, raising idle RPM. A stuck-open IAC valve has the same effect. One common misdiagnosis is the PCV valve or hose: a cracked PCV hose allows unmetered air in and looks exactly like an intake vacuum leak from the fuel trim data.

Common causes

Vacuum leak at intake hose, gasket, or PCV hoseThe most common cause. Any unmetered air above the throttle will raise idle. Spray carb cleaner along hoses to locate.
Stuck-open IAC valveAllowing too much bypass air into the intake. Often correctable with cleaning.
Throttle body gasket leakA failed gasket between the throttle body and intake manifold allows bypass air.
Carbon buildup holding throttle plate slightly openA dirty throttle body can prevent the plate from fully closing at idle.

What it costs

Throttle body cleaning$80 to $150
Vacuum hose replacement$20 to $100
Intake manifold gasket replacement$200 to $600
IAC valve replacement$100 to $300

Symptoms

High idle speed, typically above 1,000 RPM when fully warm
Engine races briefly then settles, or does not settle
Fuel economy decrease
Check engine light on
Car does not slow smoothly when lifting off the throttle

What to do next

Listen for a hissing sound with the engine running. Check the PCV hose and all vacuum hoses connected to the intake for cracks or disconnections. Clean the throttle body. If the idle is still high with no hissing found, have a shop perform a smoke test to locate vacuum leaks.

Lewis shows the actual idle RPM and short-term fuel trim live, so you can see whether an air leak is leaning out the mixture at the same time the idle is rising. Download Lewis.

Related codes

FAQ

Can a high idle damage my engine?: Not immediately, but a persistent lean condition from a vacuum leak can cause engine knock over time. Address it within a few weeks.
Why does my idle eventually come down but take a long time?: The PCM may be trimming fuel or IAC position to compensate. Once it adapts, the idle can drop, but the root cause of the extra air is still present.
Is P0507 common after replacing the throttle body?: Yes, if you did not perform the idle relearn procedure afterward. The PCM needs to relearn the new throttle body's parameters.