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Showing results for tags 'PO304 2013 Impreza WRX STI'.
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Here we go gang! 2013 WRX STI with 23k on it and it will set a po304 code. Check engine light will come on with c.c.& vdc and s.i.lights on dash. Here is a little history that i know on this car. Sold by a local used car lot with 23,000 miles on it! Still all stock exhaust system & intake & duct work & turbo and ECM ID & cal. numbers.When it came to me it has a rough idle.We brought engine up to normal temp. and performed a compression and cylinder leak down tests.Found cylinder #4 compression reading slightly low @ 125 other cylinders about 140. Cylinder leak down test showed #4 cylinder has 15% leakage into the crank case blowing air out oil fill cap. Got owners ok for engine tear down.R&R engine and disassembled for inspection , found #4 piston intact not broken! rings worn and block passed out of roundness spec's soo we replaced short block with new Subaru unit also performed a carbon & valve job.Put it all back together car running well driven 200 miles and came back to shop with the CEL on again PO304. Owner left car with us , i switched #2 & #4 coils the code stayed with the cylinder. I switched #2 & #4 fuel injectors and code stayed with the cylinder! Just to cover my BUTT i redone the compression & leak down tests,compression readings were 140 and leak down was at 2% all good! i all so ohm out wiring harness for fuel injectors and coils to ECM all readings 0.2 ohm all good.Also check ground wiring battery to engine & engine to ECM 0.2 ohm. The owner has stated to me that car runs well and idles good put here is what he noticed , with car at normal temp.and we had a couple of hot weeks 90'f + he would go to the store shut off the car and 10 mins later restart it and would have a rough idle and set the CEL (PO304) Now checking all the freeze frame data sheets and found that each time the CEL was set it was between 13 to 17 seconds after start up! With Subaru select monitor and graph the cylinder miss fire monitors would show all cylinder @ 0 % but #4 was showing up to 22% miss-fire from start up to 17 seconds of running time.After the 17 seconds of run time the monitor would show 0% on #4 cylinder and engine roughness went away! I also noticed that bank #2 exhaust VVT angle is showed -1' deg when the miss fire is happening. Bank #1 exhaust VVT angle shows 0'deg after engine restart and idle for 17 seconds. When this miss-firing is happening you can shut the car off and restart and will miss fire all over again for 17 seconds. i have this happen 5 or 6 times in a row! The real kicker is the last drive cycle last 1800 miles with no CEL. So i "m asking my Subaru Brothers and Sister for any Help!