Here I am asking for some pro insight.
The car is a 2008 Spec-B with 180000km, dont know much about its past. The main issue i'm hunting is a clear hesitation at WOT, between 3000 to 5000 rpm (like when the turbo kicks in). It happen almost every time I push it, but it is quite unnoticeable in [I] mode. Another clue is, after I fill gas, the car is hard to start. This could be related or not (but it is not my priority right now). Other than that, everything runs fine, no strange sound or anything...
What has been done already (Not all related):
Both OCVS (Had a P0021, changed both sensors)
New banjo bolt with filter on turbo side
New grounds (Battery and engine)
New Spark Plugs
I have 2 suspects right now : O2 sensor or Vaccum/Boost Leak.
I've read that a vaccum leak can be easily found by looking at the A/F Learning #1
at idle. In my case, this value goes up at 21.88% as soon as the car finish heating up and idle go down. So, is it right, I have a vaccum leak? My idle is'nt that bad and I quickly check all the vaccum line I can find and no luck yet.... It does go down when I give throttle.
Then, if I have a vaccum leak, I most likely have boost leak as well, but can this be enough to make those hard hesitation at wot?
I've been told this is a common issue on the car (also had to replace it on my previous WRX). I wanted to clean it in case it change something but it is really stuck there, even with the right tools I'm about to damage the bolt so I will wait for a "real" mechanic... But, is there any log I can make that could help prove if my O2 sensor is faulty or not?
If you have any other suggestions, you have all my attention!