A month ago I put a new engine into this car, and have been driving it gently to break it in. Yesterday I decided it was time to push the pedal a little harder, and after a short burst of acceleration the car dropped to an idle and began to have a rapidly repeating idle surge. I pulled the codes, and it appears there is an issue with the "drive by wire" components, or an idle position sensor. I pulled the codes, have a P2109 and P0638. There are 2 2109 codes and 2 P0638 codes, but they seem to be duplicates. and there is no difference in the information in them other than a timestamp.

Any tips on where I should begin in order to get the issue resolved? Thanks!!

Edited July 3, 20232 yr by ebbsspeed

Clean the throttle body and if that doesn't resolve it start by replacing the accelerator pedal assembly. They are a known failure item. 

GD

 

8 hours ago, GeneralDisorder said:

Clean the throttle body and if that doesn't resolve it start by replacing the accelerator pedal assembly. They are a known failure item. 

GD

Thanks General Disorder. I'll be out of town for a few days but will clean the throttle body when I return.

i second the pedal assembly... other half's 2006 had odd symptoms - surging idle, slow to respond, etc... replacing the pedal assembly solved it

Well, I got it fixed. When I bought this car I was told it had a bad knock, and the guy I bought it from had started to take it apart. The intercooler and a few other bits had already been removed and thrown into the back of the car.  I spent about an hour putting it back together to start it. It did have a knock that was the worst I'd heard, outside of a diesel dozer starting in cold weather. Long story short, I put a brand new short block and rebuilt heads in it, and had been driving it gently for a bit to break it in. When I finally did put my foot into it, the stuff I mentioned in the original post happened.

Based on lots of internet looking and some of the suggestions in this thread, I decided I'd try a new accelerator pedal assembly. I had the same issue afterwards, so started to pull parts to get at the throttle body. When I got the rubber boot between the intercooler and the throttle body pulled loose, I noticed the butterfly was partially open. I doused it with cleaner to see if that would free things up, but it looked fairly clean before I sprayed it. I pushed on the butterfly a bit and a "thing" that was jammed between the butterfly and body fell out, and the butterfly closed. I consider myself quite lucky that the "thing" which got blown into the throttle body when I put my foot into it never made it past the butterfly to an intake valve. I don't know if I somehow dropped this "thing" into the intercooler, or if it was dropped in there when the previous owner threw parts into the back of the car. I typically bag and label things as I disassemble something I am not familiar with, and this was my first experience with a DOHC turbo Subaru, so I was extra cautious in bagging and labelling everything I removed. 

Cleared the codes, did an idle relearn procedure, and all is well.

The "thing" was a stainless steel lock washer. 

 

 And now you know why I suggested to clean the throttle body FIRST. 

Glad you avoided total destruction. 

GD