P0507 means your engine is idling faster than the computer commanded, and the large majority of cases come down to unmetered air getting into the engine somewhere past the throttle plate — a cracked vacuum hose, a leaking intake gasket, or a throttle body caked in carbon. The code names the idle air control system, but the idle air control valve itself is far from the most common cause. Think of it as “the engine is getting air I didn’t give it” rather than “the idle valve is broken”.
What Does P0507 Mean?
At idle, the throttle plate is essentially closed, so the engine can only draw the small, carefully metered amount of air the computer allows through — via a dedicated idle air control (IAC) valve on older designs, or by holding the electronic throttle open a few degrees on modern drive-by-wire systems. The ECU has a target idle speed for the current conditions, and it watches actual RPM against that target.
P0507 sets when actual idle RPM sits meaningfully above target — commonly around 200 RPM or more over, though the exact threshold varies by manufacturer — and the computer can’t pull it back down. Almost always, that means air is entering the engine through a path the ECU doesn’t control and can’t measure.
P0507 is filed under “idle air control system”, so the obvious move looks like replacing the IAC valve. In practice that valve is one of several suspects and rarely the first. The system is reporting that it has run out of authority to lower idle speed — the reason is usually somewhere else entirely.
Common Symptoms
- Idle speed noticeably higher than normal — often 1,100–1,600 RPM where the car used to sit around 650–800 RPM.
- Check engine light on, sometimes the only clue if the idle rise is mild.
- The car creeps forward harder at a stop in an automatic, and needs more brake pressure to hold still.
- Idle that hangs when you lift off the throttle instead of settling straight back down.
- Occasionally a lean code alongside it — a vacuum leak that raises idle also leans the mixture, so seeing P0171 in the same scan is a strong hint at the cause.
Common Causes, Most Likely First
- A vacuum leak — cracked or disconnected vacuum hoses, a perished intake manifold gasket, a split intake boot after the mass airflow sensor, or a leaking PCV hose. This is comfortably the most common cause, and it costs almost nothing to fix once found.
- A dirty throttle body, where carbon buildup around the throttle plate stops it seating fully closed, leaving a permanent air gap the ECU can’t compensate for.
- A sticking or dirty idle air control valve, on vehicles old enough to have a separate one — carbon deposits hold it partly open.
- A faulty or misadjusted throttle position sensor, telling the ECU the throttle is open slightly when it isn’t.
- A stuck-open PCV valve, which is effectively a calibrated vacuum leak that has stopped being calibrated.
- A binding throttle cable or pedal linkage on older cable-throttle vehicles, holding the plate a fraction open mechanically.
How to Diagnose It
- Read the fuel trims before touching anything. A vacuum leak typically shows a positive short-term or long-term fuel trim at idle — often well beyond ±10% — that shrinks or disappears as RPM rises. That single reading points at an air leak more reliably than any visual inspection.
- Inspect every vacuum hose by hand, flexing each one. Rubber that has gone hard cracks on the underside where you can’t see it, so feel for the split rather than just looking.
- Listen for the hiss with the engine idling and the bonnet up. A meaningful vacuum leak is often audible as a steady, high-pitched hiss that changes if you briefly cover a suspect hose.
- Look at the throttle plate. Remove the intake duct and check whether carbon has built up around the edge of the plate. A visible black ring is enough to explain the code on its own.
- Check the PCV valve, which should rattle when shaken and shouldn’t flow freely in both directions.
- Only then consider the IAC valve or throttle position sensor, testing each against manufacturer specification rather than replacing them speculatively.
If the leak won’t show itself, a workshop smoke test — low-pressure smoke pumped into the intake to make leaks visible — will find it in minutes for a modest diagnostic fee. That is almost always cheaper than replacing parts one at a time hoping the idle drops.
Possible Fixes
| Cause | Fix | Typical cost |
|---|---|---|
| Cracked vacuum hose | Replace the hose | $10 – $40 |
| Leaking intake manifold gasket | Replace the gasket | $200 – $500 |
| Dirty throttle body | Clean the throttle body (and relearn idle if required) | $15 – $60 (DIY) / $80 – $180 (shop) |
| Sticking IAC valve | Clean it, or replace if it won’t free up | $20 – $250 |
| Faulty throttle position sensor | Replace the sensor | $80 – $250 |
| Stuck-open PCV valve | Replace the valve | $20 – $80 |
What usually doesn’t work: replacing the idle air control valve because the code mentions it. Plenty of P0507 cases have had a new valve fitted and returned unchanged, because the extra air was never coming through the valve in the first place. Confirm where the air is entering before buying anything — the same principle our guide to what an OBD-II scanner can and can’t tell you covers in more detail.
Can I Drive With P0507?
Generally yes, though a high idle is worth sorting out reasonably soon rather than living with. The immediate concerns are practical: the car pushes harder against the brakes at a stop, uses more fuel, and puts extra heat into the transmission and brakes in stop-start traffic. If the same vacuum leak is also leaning out the mixture, a sustained lean condition is the part that matters more for the engine — see our P0171 guide if a lean code appeared alongside this one.
When to See a Mechanic
Book it in if a hose inspection and throttle body clean don’t bring idle back down, or if the idle is high enough that the car creeps strongly in gear. A smoke test is the efficient next step and most workshops can do one quickly. If the high idle comes with stalling, surging, or hesitation instead of steady fast idle, our guides to a car that dies at idle and a car that shakes at idle cover those separate patterns. More in our trouble codes section.
Frequently Asked Questions
What does the P0507 code mean?
Your engine is idling faster than the computer commanded and the idle air control system can’t bring it back down — usually because unmetered air is entering the engine through a vacuum leak or a throttle plate that isn’t seating fully closed.
Is a vacuum leak really the most common cause of P0507?
Yes. Cracked vacuum hoses, perished intake gaskets and split intake boots account for the large majority of cases. Checking fuel trims at idle is the fastest way to confirm it — a vacuum leak typically pushes them well positive at idle and less so at higher RPM.
Will cleaning the throttle body fix P0507?
Often, if carbon buildup around the throttle plate is what’s holding it slightly open. Some vehicles need an idle relearn procedure after cleaning before idle settles properly, so check whether yours does.
Is it safe to drive with a P0507 code?
Usually yes in the short term, but the car will creep harder in gear at a stop, use more fuel, and should be fixed before long — especially if a lean code such as P0171 appeared at the same time.
How much does it cost to fix P0507?
Frequently very little — $10 to $40 for a cracked vacuum hose, or the cost of a can of cleaner for a dirty throttle body. An intake manifold gasket is the expensive end at roughly $200 to $500.
