The P0507 code in your 2017 Honda Accord indicates that the idle speed is higher than expected—specifically, RPM is above the target idle speed by 200 or more. Combined with surging, this points to the ECM struggling to control idle properly, often due to air or vacuum issues.
Understanding P0507
The ECM maintains idle speed by controlling the electronic throttle body opening. P0507 triggers when the actual idle speed exceeds the target by a significant margin. This often happens when extra air enters the engine that the ECM didn't meter, causing the engine to run fast.
Common Causes of High/Surging Idle
Vacuum leaks allow unmetered air into the engine. A dirty or sticking throttle body affects idle control. The Idle Air Control (IAC) valve or electronic throttle has issues. Intake manifold gasket leak. Faulty coolant temperature sensor reports incorrect temperature. PCV system malfunction.
Why Surging Occurs
Surging happens when the ECM tries to correct the high idle but overcorrects, then the extra air causes the idle to rise again. This creates a cycle of correction attempts that you feel as surging—idle bouncing between high and low.
Diagnostic Steps
Listen for vacuum leak hissing. Check throttle body for carbon buildup affecting blade movement. Verify coolant temperature sensor reads accurately. Inspect PCV valve and hoses. Using Honda HDS, monitor idle adaptation values and throttle position. Smoke test the intake system to find vacuum leaks.