This is NOT a Legacy, this is a question a out my friends Impreza. I own a Legacy and have been lurking in this forum for years. You guys are fantastic and never lead me wrong. Hoping you guys are willing to help.
My friend let the original ej253 die in his 2006 Impreza. He bought a JDM ej253 to replace it. Install went easy enough. At high rpm (5000+) the car throws P0302 and P0301 and goes into gimp mode.
We've tried everything random thing we can think of-
Changed Spark plugs/wires
Changed coil pack
Changed cam angle sensor
Changed crankshaft sensor
Changed fuel pump
Changed VVT valves
Cleaned MAF sensor
Used 2 bottles of sea foam to clear the carbon build up. Cylinder 2 had the most.
Valve cover gasket
Adjusted valves
Checked for vacuum leaks
Replaced PCV Valve
Replaced O2 sensors (pre/post cat)
Compression test results-
C1: 155
C2: 170
C3: 160
C4: 155
Originally had the USD wiring harness, switched to the JDM harness.
Still throwing codes! And I've exhausted my idea bank. Is there something I'm missing?
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