This has had me scratching my head for a while now. I have searched all the forums, and have yet to find the solution.
Completely stock 2006 WRX TR, 5 speed manual
When accelerating, either fast or slow, the car has no power or is intermittent. Almost to the point where it won't accelerate at all. Then, when it gets to 3500-4000 RPM's, it takes off. A safe bet here is that the turbo is spooled up and giving me the power I am used to. It will do this in all the gears at all speeds. Sometimes I have to get the RPMS up in the turbo area and let the clutch out in order to accelerate. Certainly not good for the clutch, but beats taking 5 seconds to get through an intersection.
Solutions tried after reading through multiple forums:
1. I replaced the upstream O2 sensor, but had no change.
2. Replaced the MAF sensor, but had no change.
3. Realized that I did not follow the manual verbatim and did not disconnect the battery when swapping the sensors. Thought it was more of a safety thing, but turns out this also resets the ECU. So I reset the ECU, and BINGO! Car runs great, and with all the power it use to have. Until about 100 miles later when it started doing it again. It starts out mild, and then it slowly gets worse over days of daily driving. Looked for vacuum leaks with carb cleaner, and have not found any.
4. Reset ECU again, and it is running good again. However, my guess is that in the next 80 miles or so it will start doing it again.
Any thoughts on this? My conclusion is that resetting the ECU clears out the bad data my car is learning from some inputs. The question is, is there a bad sensor, or a mechanical issue? And, where do I look next?