Mitsubishi Eclipse P0505: Idle Air Control System - Malfunction

P0505 An OBDII Code that addresses the idle air control system within the Mitsubishi Eclipse.  It’s a generic code, which means that it has the same meaning for the Eclipse as it would any other vehicle (Eclipse or not).

P0505:  Idle Air Control System:  Malfunction

P0505 triggers when there is either a stuck or clogged idle control valve or a vacuum leak.  However, there are other possible causes.  Although, they aren’t as prevalent.

P0505 Mitsubishi Eclipse


Índice de Contenido
  1. P0505 Symptoms:  Mitsubishi Eclipse
  2. Eclipse P0505 Causes
    1. Valve for Idle Air Control
    2. Vacuum Leak
    3. Carbon Buildup
  3. Conclusion

P0505 Symptoms:  Mitsubishi Eclipse

This particular trouble code lets you know that there is something wrong with the idle air control system, but that’s about it.  These symptoms could be different.

These are the top symptoms of P0505.

  • Engine service engine will soon be light
  • It is a rough idle
  • Stalling
  • Very high idle speed 


Eclipse P0505 Causes

P0505 can usually be caused either by a vacuum leak or an issue with the idle control valve.  While replacing the idle air control valve seems like a good idea, it’s worth your time to check for a Leakage of vacuum first.

Mitsubishi Eclipse P0505 Diagnosis

Valve for Idle Air Control

The idle air control valve’s primary job is to regulate the idle speed of your engine.  The idle air control valve regulates the engine's idle speed by controlling the amount of air that is allowed in.

You can either get the IAC valve stuck or dirty.  It may be necessary to replace it or clean it.  Here’s a great You Tube video Here are some tips on cleaning an idle valve.  

They are available if you decide that an idle valve control valve is needed. It is very affordable.


Vacuum Leak

While the idle air control valve is often the cause of P0505, it’s a great idea to start diagnosing it by looking for a vacuum leak.  Check the vacuum tubes surrounding the IAC.  You may need to replace the vacuum tubes around the IAC if they are cracked or dry rotted.

You can code the Eclipse code to throw these codes by leaking around your throttle body, or intake manifold.  Here’s a great article from Popular Mechanics on How to locate a vacuum leak.


Carbon Buildup

It is possible for carbon to buildup in the IAC intake area.  It is possible to fix this problem by checking the IAC inlet area for blocked passages.

The throttle body can become too dirty to allow air to enter the engine.  You can even throw P0505.  Often, when this is the case, you’ll feel the engine stall for a second before it recovers when slowing down.  

This happens because the engine can’t adjust to this problem fast enough.  It is possible to fix the problem by cleaning it from around the throttle blades.



You will be able to diagnose P0505 on your Eclipse.  Most of the time it’s a vacuum leak or the idle air control valve.  If you feel like there’s anything that you can add, please feel free to leave a comment below.

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