The car throws this CEL code P0505 for a month. Went to the mechanic, said it was the IAC valve.
Ordered the MD628318 part, first one that arrived had the smaller head, sent it back. Yesterday I received the correct part, the mechanic replaced it, cleared the CEL. He didn't reset the ECU though...
No CEL on board until the evening, when I left the office. On my way home, the darn CEL came up again.
I couldn't be more pissed... What else can generate that code? How can I find out? Could be a boost leak or...?
Any help will be appreciated. Thanks!

 

Found this for you.
CEL = P0505 = Idle Air Control Motor (IAC) circuit condition or idle speed higher/lower than expected.

Definition: IAC circuit condition or idle speed higher/lower than expected.

Explanation: The ECM has detected that the IAC counts are higher or lower than expected, the engine speed is not its expected range.

Probable causes:
1- Vacuum leak on the engine
2- Dirty throttle body
3- IAC motor is defetive
4- Poor electrical connection to the IAC valve.

I got this after install the catch can (I removed the throttle body and manifolds). Went back unplugged, and re-plugged everything, checked for boost leaks, made sure everything is seated properly, and checked the tightness of all of the screws. Reset the code by unplugging the battery and I haven't got it since (300miles ago). IMHO I'd start there.

 

^ nice wish i had a explanation like this for all my problems

 

Hello, thank you for such a detailed answer. Well, the IAC is brand new and just replaced. Truth is the mechanic didn't reset the ECU after changed it nor did he adjust the idle speed in any way.

I will go with the car to the mechanic and start all over again.

Thanks again!

 

I am having a similar issue. I recently had my intake manifold and throttle body ported and while everything was off I removed the EGR system. I capped off everything on the IM from the EGR and installed the blockoff plate. Now the car starts and idles fine, but the second I get into boost I get the P0505 code. I can drive around all day without getting into boost and no error code. I've removed the IAC and made sure the seal is installed properly and the connector is tight. Any ideas?

thanks,

 

OK, last year I went through this for like two months without any fix. I've ordered a brand new IAC valve from U.K., replaced it, the garage mechanic cleared the CEL... only to have it back on board 15 minutes later, after the first WOT.

I was about to give up - as a last solution I took a ride to the Mitsubishi dealer service to have the car checked. 30 minutes later it was absolutely fine, the CEL never came back.

In my case, it was the air-flow meter, they checked it and adjusted as I was told. Have that thing inspected by a qualified technician in your area if you can.

HTH
Andrei

 

any other ideas? Could it be a tuning issue? Could it have something to do with removing the EGR?

 

Probably not the IAC/ May be a vacuum leak causing a raised idle.

 

That seems to be the common cause. I've looked it over and over and could not find any leaks. Could removing all the EGR without updating the tune to "pass" the EGR test cause this?

 

Usually you would get a p0401 or EGR code if that was done.