P0505 - Idle Air or ECU?

[pgarland]

OK, I have searched and searched, and am looking for opinions here. My car has been acting goofy, and just the other day it spit out the P0505 code (which usually means bad IAC, but I'm looking for some expert advice). Here are the symptoms of what the car has been doing:

The whole car shuts down and immediately starts back up (like within a half second or so), this only happens when car is in Drive (its an Automatic) and I am moving, usually when I'm slowing down for a stop sign or stop light. It seems to happen more often when I am running the A/C, stereo, headlights, or any other electrical accessories (as in it'll happen to me a few times in a 5 minute period, versus only happening once or twice in a 5 minute period if I have everything else shut off). The idle seems fine when I am in neutral or just sitting, I only seem to have the problem when the car is moving. Problem is intermittent (some days it happens a few times, other days not at all). Also, after one of the "surges" (for lack of a better word to describe it) I immediately shut down my radio, and since then my amp and subs will not power up and play (I suspect this is more to do with a fuse or something though, I am not too concerned about this at the moment).


Now I know it very well could be the IAC, but am looking for any other recommendations before I go and blow 80 bucks on a new one. I am sure my EGR is either bad or going bad, and I have the block off plates for the EGR, I just haven't blocked the EGR yet because I want to be able to see if the car throws any more codes (a blocked EGR will throw a permanent CEL, which means I wouldn't know if any new codes were being thrown without an OBDII reader). Could a bad EGR be the culprit? I removed and cleaned the throttle body and IAC a couple of months ago, and there are no vacuum leaks in the car. I have heard and read that it could possibly be the ECU, whats the best way to verify that the ECU is good? Any other suggestions? Thanks in advance.

 

[99BoostedRS]

Well what you can do for the IAC valve is to take out the TB and with all the connectors installed turn the key to "on" but dont start it(check the IAC while someonelse turns the key)and see if the IAC moves at all. I can't help with the EGR because i dont have experience with blocking it off or even doing anything to it sorry.

 

[rstare]

Check the IAC as Boosted said. Really, the only way I know of checking an ECU is to either rule out everything else, or switch it out for a known good ECU and seeing if that changes anything.
However, as you mentioned, it really sounds like the IAC.

 

[pgarland]

Alright, a little more searching brought up this chart:

You must be logged in to view this image or video.

from this thread: http://www.dsmtuners.com/forums/newreply.php?do=newreply&p=152142924

I'll be checking the IAC this weekend, and I'll update further with the results. Thanks for the replies.

 

[pgarland]

Resolved, it was the IAC. Thanks guys.