Only replace what is needed. You probably didnt need an o2 sensor but hey, old ones dont send out signals as fast so hell, why not.

How is your car idling?
Any boost leaks?
Any issues with your engine?

yes i need an o2 sensor since thats what came up when i scanned the ECU, alongside the coolant temp sensor. This new cel came up after all that was fixed. Boost leaks, i dont htink i have but since i last tested it, i did remove my UICP so i will do another test. My idle is a little screwie. Moves up and down a small hair and sometimes will go up to about 1500 and then settle down.

What exactly is the code from the ECU? Many times the generic scanners don't translate the codes correctly.

P0505 idle system control malfunction

Black95TSIawd said:

P0505 idle system control malfunction

Click to expand...

my check engine light gave the same code. i recently went from venting to recirculating. i thought that was the reason why my check engine light came on. i don't know why, i was hoping i guess. my rpms go up and down also. but i have notice the same problem on my oil gauge. could they be related or seperate issues?

From what I'm reading, P0505 is IAC valve system fault. Perhaps replace the IAC?

I recently got the same error code, anyone know what the solution is?

Do you have a logger? If you do, check your fuel trims and o2 volts at idle and see if they are ok. Is your idle jumpy or high/low consistantly or just on warm-up?

If everything seems fine, remove your ISC under your throttle body and test the resistance. If its dead, I have a few spare ones that work...PM me.

Brandon, I'm convinced yours is just too much fuel after we got rid of your shitty fuel filter we'll get it fixed tomorrow

I've been having the same problems. I had 4 error codes, I changed my O2 sensor, now I have 3 codes.

P0505-Idle control system malfunction
P1104-Turbocharger wastegate soleniod malfunction
P1400- Manifold differential pressure sensor circuit malfunction

I've been having trouble pinpointing some of theses as well

car has idle surges too, like you explained before.

Idle is jumpy mostly at warm up, but dosn't always do it.

it has a mind of its own.

I also have a P0505 code coming up. Anyone know how much it is to replace the IAC Valve? I've been way to poor to do it for a while but I'm getting sick of it so help us out!

Will CEL code P0505 affect a vehicle's performance? My guess would be no, but I am not certain. Everytime I clear mine, it comes back within 24 hours...... Perrformance doesnt seem to change with it cleared/uncleared.

Is it true that a rich idle can cause this code to pop up? I know I have a rich idle (and mid, and wot ), but my idle is smooth. I'm going to lean it out a bit and clear the code to see if it comes back.

I have that same CEL. After taking out my emission lines, capping everything off, putting on David Brode UICP, and installing Greddy boost controller, it was fine for a few days. And then I put on the K&N FIPK and later that day it went on. I am not sure what this could be, but if someone could find out, I would really really appreciate also. I have checked everything over and over. I don't know what it could be. My car idles better than before and everything is fine. Someone help, please and thanks.