nwoutback99 Posted February 10, 2016 Share Posted February 10, 2016 Alright...I have been lurking on this messageboard for about a year trying to figure out an issue my car has been having so I finally signed up. Any help would be much appreciated! So my 99 legacy outback (with 175k miles) has been stalling every time I approach a light or have to idle. When I first start it the idles fine, but the more I come to a stop the idle lowers each time until it dies and the CEL comes on. It pulls the p1507 code for the idle air control valve and a code related to the knock sensor. Now following what I can see other people have done, I pulled the IAC off twice and cleaned it replacing the gasket the first time. I also sea foamed it...no help. Next, I replaced all of the filters and checked for vacuum leaks no luck. After that, I cleaned the MAF sensor really well with MAF cleaner still no luck. Replaced the spark plugs to no avail...any ideas? Originally this problem was intermittent but now it happens every time I drive it. Quote Link to comment Share on other sites More sharing options...
AdventureSubaru Posted February 10, 2016 Share Posted February 10, 2016 Start with a new knock sensor. They fail regularly and are super easy to replace. The $10 ones on ebay do just fine. Second to that, I would check your mass air flow sensor. Clean it and see if that helps. Replace it to be sure. They will cause the car to get buggy, lose power at random and stall out without throwing a code. Quote Link to comment Share on other sites More sharing options...
mikaleda Posted February 10, 2016 Share Posted February 10, 2016 Replace your IAC Get a used one from a junkyard, clean it up and install with new gasket. Quote Link to comment Share on other sites More sharing options...
nwoutback99 Posted February 10, 2016 Author Share Posted February 10, 2016 I have a new knock sensor on the way luckily so will try that. Thanks for the help! Quote Link to comment Share on other sites More sharing options...
dp213 Posted February 17, 2016 Share Posted February 17, 2016 I agree mikaleda, replace the iac. Quote Link to comment Share on other sites More sharing options...
nwoutback99 Posted March 23, 2016 Author Share Posted March 23, 2016 So I replaced the knock sensor it helped but didn't fix the issue. I just recently ran into someone parting out a 2000 legacy outback are the IAC valves the same or did they change them? Quote Link to comment Share on other sites More sharing options...
gravitate Posted March 23, 2016 Share Posted March 23, 2016 I apologize if this response double or triple posts, having internet issues. For over a year I had the same issues as you with the same code along with a knock sensor code. It was less frequent though. I replaced the cracked knock sensor but what did the trick was actually replacing the Neutral Safety Switch on the side of my transmission (5spd). From what I understand, that NSS shares the same circuit as the IAC. It makes sense too if its dying when or right after you push in on the clutch if you have one. So I would try that if the IAC doesn't work. Good luck Quote Link to comment Share on other sites More sharing options...
gravitate Posted March 23, 2016 Share Posted March 23, 2016 Ferret posted this on another thread yesterday:This is a switch on the side of the manual transmission, like the backup light switch. Dealer only item, pretty inexpensive and easy to change. High enough on the trans that you will not leak any fluid. Purpose, , to tell the ECU when you are in Neutral, so either you are decelerating or the ECU must control the Idle. Example, you are driving WITHOUT your foot on the gas, Car in gear, The ECU doesn't have to control the idle. You shift into neutral, NOW the ECU MUST control the idle. It's detected as a fault when the switch is bad ... you are IN GEAR, without foot on the gas, but the ECU DOESN'T KNOW IT, so the ECU now tries to control the idle AND IT CAN'T. So it thinks it's at a HIGH UNCONTROLLABLE IDLE. Older manuals usually call out IAC , TPS and other Idle controls for this error. 1 Quote Link to comment Share on other sites More sharing options...
mikaleda Posted March 23, 2016 Share Posted March 23, 2016 So I replaced the knock sensor it helped but didn't fix the issue. I just recently ran into someone parting out a 2000 legacy outback are the IAC valves the same or did they change them? Nope they are different Quote Link to comment Share on other sites More sharing options...
mikaleda Posted March 23, 2016 Share Posted March 23, 2016 I apologize if this response double or triple posts, having internet issues. For over a year I had the same issues as you with the same code along with a knock sensor code. It was less frequent though. I replaced the cracked knock sensor but what did the trick was actually replacing the Neutral Safety Switch on the side of my transmission (5spd). From what I understand, that NSS shares the same circuit as the IAC. It makes sense too if its dying when or right after you push in on the clutch if you have one. So I would try that if the IAC doesn't work. Good luck That's interesting, definatly something worth looking into. First time I've heard of this problem. Quote Link to comment Share on other sites More sharing options...
nwoutback99 Posted April 14, 2016 Author Share Posted April 14, 2016 Got a hold of the nss and a buddy let me use his lift swapped it out only got to drive it for a little bit tonight no codes though and it didn't stall. will report back when I have more info. Thanks for the help everybody! Quote Link to comment Share on other sites More sharing options...
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