So I replaced my IAC valve about 2 months ago and everything was fine until I started up me car yesterday and it wouldn't hold an idle. I had to keep my foot ok the gas petal until it warmed up. I also then pulled a p0505 code which is the iac.

I then went to drive it and noticed a loss of power pretty much throughout the whole band and especially about 3k rpm. Feels like the turbo isn't kicking in as much as it should be.

My question: is this because of the IAC or is something else wrong that may have tripped the p0505 code. I did some research and maybe it's a boost leak or vacuum leak? Please help because I am afraid to drive my car is there is something terribly wrong.

P.S. I should mention I took out the iac valve and cleaned it and it looked fine but my car is still running crappy after replacing it.

 

Yea I'm 99% sure its a leak dnt really trust scanners that much cuz they can't detect things Like this.. Do a boost leak test i had da exact problem

 

Alright well I'm going to try to change the iac anyways cause its under a warranty since its still new. I'm hoping that will fix the idle at least. Could the boost leak also cause the idle problem or just the power loss?

 

If the leak is bad enough, you're likely to experience everything you mentioned. Do a boost leak, and also check the MAF.

 

So I just replaced the iac and it idled up fine but now the idle won't come down once it's warmed up, it just stays stuck around 2k rpm. So I took it for a test drive and when I stop drops to 1000rpm then back up to 1500. Then up then down then up then down quickly, until it finally goes up to 2000 again and stays. Is this from a boost leak???

 

vacuum leak. tb shaft seals? also remove the UICP and make sure the throttle body does not have residue where the butterfly closes and opens

 

Well I just took it to a shell station where I trust a guy who knows about these cars and they're going to try a boost leak test and just test for vacuum leaks in general. Needed an oil change anyways so I figured I just let them take care of it. We shall see...

 

let us know what he says

 

Check your maf sensor . I'd say you probably have a huge boost leak somewhere . Possibly could be your oil feed line to your turbo also check and see if there's any oil anywhere

 

i had this happen to me a few months ago, high idle and all, it was the throttle body shaft seals, one i replaced those, with a new IAC my idle went back to normal, also remeber to disconnect your battery when swapping out electrical stuff.

 

Check the vacuum hoses on the intake manifold. Specifically the one that runs from the manifold to the DV/BOV.

 

Well apparently one if the screws fell out of the iac. I guess I messed up when tightening all of them, probably cause i was in a hurry. Oops :-/... This cause another screw to be loose as well he said so they installed a new screw and tightened them all and he said that did it.

 

This is still a possibility though cause I was unable to finish talking to the mechanic cause he was gone but he didn't write anything about a boost leak test on the receipt, only the checking of the iac. Ill check this tomorrow morning cause its driving fine but I still feel it to be a little sluggish...maybe it's in my head, idk but I do know there is a bit of oil on the driver side of the engine on and around where the thermostat housing is. I believe I may also have an exhaust leak so I'm goin to install a new exhaust gasket and see how it goes. At least my idle is fixed though!

 

So, i had a feeling that i still had a boost leak after all of this and I just installed a boost gauge. At idle the vacuum is only around -13. I know that is should be around -18 or so when stock so I checked all of my air hoses to the turbo and intake mani and couldn't find and holes.

Any idea what else to check before doing a complete boost leak test as I don't yet hve the tools or time for this?

Just FYI just in case these mods may change anything with the vacuum I have: turbo back exhaust w/ down pipe and a
K&N intake with upper and lower inter cooler piping

 

Well if u have a problem with the idling, I'd get my hands on a scanner or laptop with datalog capabilities not a code reader, if your idle isn't coming down I'd look into maybe a faulty tps sensor.....that one is somewhat easy to check, check the volts at idle with it. It's on the side of your throttle body.... That could be bad or if your boost leak test was done right, it'll tell you if you have a leak at your throttle body seals as well.....good luck...I hate boost leaks myself..haha