Acceleration Problem with 2005 JDM WRX

[Mikku]

Under hard acceleration I’m experiencing some, what I would describe as stuttering of power around and about the 3,000RPM mark. It’s like the engine won’t accelerate beyond that point, so I usually back off and either try again (which sometimes works) or change up instead. It doesn’t happen every time and is most noticeable in 3rd gear, though sometimes happens in 2nd and 4th. I’m no mechanic, so don’t know where to start but if I had to guess, I would say it’s electrical or fuelling-related.

I’ve had the car for nearly two years now and this has only started to happen during the last few months. No engine codes are showing, so I’m after some advice on what this problem could be or at least where I should start looking first, before I pay for someone else to look at it. Thanks in advance for any ideas or suggestions. 👍

[Tidgy]

has the car been mapped for uk fuel? could be the cold weather is causing the issues.

[Mikku]

Sorry, I should have said, I'm in Japan. I've been reading about the numerous things it could be. I had new spark plugs and coil packs fitted last year, about 30,000km ago, so they should be okay. The car's due a fuel filter change, so I may see if that does the trick along with making sure that all of the ground wires are properly earthed.

[Mikku]

Forgot to update this, so better late than never, I managed to track down the problem to a dirty MAF sensor. Before I could try any of the ideas mentioned above, an engine check light came on. In trying to get rid of that, I bought some MAF sensor cleaner and gave the sensor a good spray and although the check light stayed on, the engine stutter stopped, and the engine started pulling smoothly again. Below are a couple of pics of the sensor before spraying it.

The engine check light turned out to be a P0031 code, which was an O2 sensor, so that got replaced by my local dealer. 👍