01 Forester IAC swapped and idle isn't improved

[AnutherSoob]

hi everyone. I'm looking for help with the idle air control valve on my car. I've been procrastinating replacing the IAC for about 18mos. My mechanic has cleaned it and it improved for about a year. Since this seems to be a straightforward repair, I decided to buy a new IAC and replace it myself. Two screws and clip, what could go wrong? I was able to find a new genuine Soob IAC for under $320.

 

Upon installing it the engine has raced and sputtered. When stopped during the test drive, the engine would rev to 4k rpm and then drop to 2.5k rpm for a few seconds before racing back to 4k. It did this several times. It also would jerk when I let my foot off the accelerator the way u would expect when driving in the top of a gear. It is a 5spd trans, but I wasn't trying to strain the engine in anyway.

 

Do I need to put the original part back on? With the original part my car idles rough, the engine might race (2.5k rpm) for a few moments upon starting, but then it calms down closer to 1k rpm. When driving with the original IAC I'm experiencing stalled engine when I stop or it barely maintains a too low idle.

 

Please help if you can. I really need my car working well again. And I'm broke which is why I'm not in a shop with it for this issue. I needed this repair to be a simple plug and play and it's just not like that at the moment. I've owned this car for 10yrs and need to get a few more out of it if I can.

 

Thanks in advance

[Fairtax4me]

Is it the round style with the cone?

Did you replace the o-ring that goes on it?

[AnutherSoob]

Yes, it is. The new one came with a new o ring already in position for use.

[destey]

Did you remove the throttle position sensor to gain access to the IAC? That is very touchy as far as adjustment.

 

If its not that, it could be a vacuum leak (mine did the same thing and it was the gasket). Spray some carb cleaner around that area and if its sucking air in, it'll suck in the carb cleaner and cause the engine to sputter giving away the leak location.

[AnutherSoob]

Thx destey, I did not remove the throttle position sensor. I will give your suggestion a try tho.

[Fairtax4me]

Make sure the o-ring didnt get cut or damaged.

It does sound like you have a vacuum leak somewhere. Has any other work been done recently?

 

You might also try unhooking the battery for 20 minutes or so to reset the ECM. Sometimes when changing components the ECM can't respond properly to the new parts because it has altered its setting due to wear of the old parts. After reconnecting the battery start the engine and allow it to idle. Do not touch the throttle to keep engine speed steady. If the engine stalls just restart and continue idling until the radiator fans turn on, then turn back off. Turn off the engine, restart, then go for a short drive.

Edited August 14, 2015 by Fairtax4me

[juliodoodman]

Interesting!  I am going through the same or similar problem...  My 2003 Forester has been idiling erratically and high.  At minimum, it would idle roughly, the needle bouncing around 1200-1500 rpm.  With more driving, the engine would, with no pressure on the accelerator pedal, repeatedly rev up to 3000 to around 4000 rpm, sometimes even staying at those high rpms for a while.  I've never had the car stall, though.  When I would unhook the battery for 20 minutes and then hook it back up and turn the car on, it seemed to idle fine for a while, but after driving for a bit, I got erratic and high idling again.  Still no stalling, though.  I checked the codes and got P15-14 (Throttle Body Performance), P0113 (Intake Air Temp Sensor High Input), P0032 (O2 sensor heater circuit high), and P0519 (Idle Air Control System Malfunction).

 

Today, I cleaned the IACV and reinstalled it.  No difference.  I still need to check the codes again after reinstalling and disconnecting the battery.  I did notice, though, that the gasket has some damage.  Perhaps it is a vacuum leak.  I will try your method later today or tomorrow and let you all know of my results.