P2109 and P0638 recurring issue

[jayydubbb]

My 07 STI has been having intermittent throttle body related issues. I rebuilt the motor completely, drove the car about 150 miles, then as I'm sitting at a light, idle gets rough, CEL comes in and it goes into limp mode. I clear the code, drive home without an issue, but it came back intermittently after that. At that time P0638 was the only code that came up. I replaced the TB, drove 400 more miles with no further issue. I come out to my car the other day to leave and suddenly it's doing the same thing, this time with both aforementioned codes. The TB I bought was used, but I find it hard to believe that it suddenly failed just the same way that the old one did. I am at a loss here. I have tried idle relearns, messing with and cleaning all connectors, and all the other usual checks. I read up on this and it's not an unheard of issue, but there's no clear explanation as to what the fix is. The car has a catted DP, TGV deletes, turbo inlet and some other small mods that it is not yet tuned for since I am still breaking it in, it just has codes deleted for the TGV's and air pump. I do not believe it is tune related. I should also mention that when I was disassembling the motor I broke the factory TB connector since the plastic was very old and brittle, I ended up buying a new one and repinning it without any issue, everything looks good on both ends of the connector.

There is no consistency to how the issue presents itself either. Sometimes I will clear the codes and it will start normally for a few seconds, then throw the codes, sometimes the codes appear before I even start the engine, sometimes it's one code, sometimes its both. It's making it really difficult to pin down the cause. Any suggestions other than replacing the throttle body again would be appreciated.

* Registered users of the site do not see these ads.

[Jedi03]

sounds like a need to go down the trouble tree...verify continuity across the wiire harness, voltage, battery condition, grounds, ecu software version...i just replaced my corolla ecu due to a vvt issue that would randomly come and go...

[jayydubbb]

Originally Posted by Jedi03

sounds like a need to go down the trouble tree...verify continuity across the wiire harness, voltage, battery condition, grounds, ecu software version...i just replaced my corolla ecu due to a vvt issue that would randomly come and go...

I should've also mentioned that the battery is about 4 years old, well beyond what I expected it to last for, but I have a hard time believing that that would suddenly fix the issue, the car has had no other electrical gremlins besides this.