The 2017 Lexus IS should idle smoothly and consistently, but when idle surging accompanies P0507 indicating idle RPM higher than expected, the engine management system struggles to maintain stable idle speed. This code points to specific areas requiring investigation.
Understanding P0507
P0507 sets when idle speed exceeds the ECU's expected range even after the system attempts to correct it. The ECU controls idle through the electronic throttle, and when outside factors cause idle to rise, the system flags this deviation. Surging occurs as the ECU fights to bring idle down while the underlying cause keeps pushing it up.
Common Causes of High Idle
Vacuum leaks allow unmetered air to enter the engine, raising idle speed as the ECU compensates. A sticking throttle body prevents proper blade closure. IAC (Idle Air Control) circuit issues within the electronic throttle affect idle control. Air leaks around the intake manifold gaskets are common on higher-mileage engines.
Diagnostic Approach
Perform smoke test to identify vacuum leaks in the intake system. Inspect throttle body for carbon buildup preventing full closure. Monitor idle air control data through the scan tool. Check for disconnected or cracked vacuum hoses. Examine intake manifold gasket areas for air intrusion.
Repair Solutions
Address vacuum leaks with appropriate repairs—hose replacement, gasket renewal, or connection tightening. Clean the throttle body if carbon buildup is present. Perform throttle body relearn procedure after cleaning. If the throttle body is mechanically faulty, replacement may be necessary.