The three-cylinder engine in your 2021 Mitsubishi Mirage inherently produces more vibration than a four-cylinder due to its firing order. But when a P0507 code appears—indicating idle RPM higher than expected—along with increased vibration, something is disturbing the engine's idle control system. Understanding this relationship helps pinpoint the cause.
Understanding P0507
P0507 means "Idle Air Control System RPM Higher Than Expected." The engine computer monitors idle speed and expects it to stay within a specific range (typically 600-900 RPM). When idle consistently runs above this range, the code is set. Paradoxically, the high idle can sometimes cause vibration as the engine hunts or surges.
Symptoms Accompanying P0507
- Higher than normal idle speed
- Idle fluctuating or surging
- Increased vibration at idle
- Engine feeling like it's working hard at stops
- Check engine light illuminated
- Possible stalling when coming to a stop
Common Causes of P0507 in the Mirage
Vacuum Leak
Air entering the intake system after the throttle body causes the engine to run lean. The computer opens the throttle more to compensate, raising idle speed.
Solutions:
- Inspect all vacuum hoses for cracks or disconnections
- Check intake manifold gaskets
- Use smoke testing to find hidden leaks
Dirty Throttle Body
Carbon buildup on the throttle plate and bore restricts airflow control. The computer may hold the throttle more open to achieve desired airflow.
Solution: Clean throttle body with appropriate cleaner.
Idle Air Control Issues
Electronic throttle systems use the throttle body motor to control idle. Malfunctions can cause improper idle speed control.
Solutions:
- Throttle body relearn procedure
- Throttle body replacement if motor or sensor failed
Air Intake Leak
Cracks in the air intake tube or loose clamps allow unmetered air into the engine.
Solution: Inspect intake tube, tighten clamps, replace if cracked.
EGR Valve Stuck Open
If equipped, a stuck-open EGR valve introduces exhaust gas at idle when it shouldn't, affecting idle quality.
Solution: Clean or replace EGR valve.
Why Three-Cylinder Engines Vibrate More
The Mirage's 1.2L three-cylinder engine fires in 1-2-3 order with 120-degree intervals. This creates an inherent imbalance that four-cylinder engines (with 180-degree intervals) don't have. Mitsubishi uses balance shafts and careful engine mount design to minimize vibration, but some vibration at idle is characteristic of the design.
Diagnosis Steps
- Scan for codes: Confirm P0507 and check for additional codes
- Check idle RPM: What is actual idle speed? (Use scan tool)
- Listen for hissing: Vacuum leaks often make audible noise
- Inspect vacuum hoses: Visual check for cracks and connections
- Check throttle body: Inspect for carbon buildup
- Smoke test: Professional test for hidden vacuum leaks
- Perform relearn: Clear codes and perform throttle relearn procedure
Repair Costs
- Throttle body cleaning: $80-$150
- Vacuum hose replacement: $50-$150
- Intake manifold gasket: $150-$400
- Throttle body replacement: $300-$500
- EGR valve cleaning/replacement: $150-$400
- Professional diagnosis: $100-$150
The 2021 Mirage is covered by Mitsubishi's 5-year/60,000-mile warranty. Idle control issues within this period should be covered.