rwbrens Posted September 14, 2015 Share Posted September 14, 2015 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! Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 14, 2015 Share Posted September 14, 2015 No misfires on cold starts? Only misfires on warm start? Does misfire occur while the ECU is in open loop? Then go away once it hits closed loop? Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 14, 2015 Share Posted September 14, 2015 (edited) any sign AT ALL that parts have been pulled-off and re-installed? does a 13 still have aircut valves? kinda sounds like that air pump and those valves which are active at start-up. does a 13 have TGVs? is it possible the vane for cyl 4 could have a problem/be loose? also, is there any possibility the previous owner tried to flash a tune onto the ECU and the process was corrupted? You may need to find a 'stock' flash image to put into it. those are my guesses. Edited September 14, 2015 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
rwbrens Posted September 14, 2015 Author Share Posted September 14, 2015 Thanks for the good words gang ,yes the miss fire only happens when normal temp.i be leave it is in closed loop at this time because it was driven about 8 miles. bring it back into shop & shut it off for 10 mins. ( hot soak ) restart engine , roughness monitors show #4 cyl. missing to 20 % other cylinders showing 0 % Yes Lucky it does have both air pump system & TGV 's. I do know that air pump system only works on cold start up for about 15 or 20 seconds just like on this model sti. I didn't look at the TGV 's when i had the intake off when i did the short block. I think i can take off the throttle body and bore scope the intake runners to see if the TGV's are intact or loose.Subaru Tech line stated the ID &Cal. numbers in ECM are all OEM. Today i found a reflash for a high rev. condition , tech line stated try the re-flash. i did no change! Today i also put a vacuum gauge on the intake it was reading 18" vac. and steady! also pinched off the vac. hoses for brake power booster and fuel pressure regulator, one at a time with no change! Tech line also stated that - 1' exhaust vvt cam shaft is not enough to cause this miss.Thank Ralph Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 15, 2015 Share Posted September 15, 2015 (edited) man, you are thorough - way ahead of me and my w.a.g.s I had to reflash my ecu to kill 14 codes for stuck (closed thank god) aircut valves. (but, 06 WRX) Edited September 15, 2015 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 16, 2015 Share Posted September 16, 2015 Most cars still run open loop for a few seconds even on a warm restart. O2 sensors can cool below operating temp in just a few minutes and have to re-heat when the engine is restarted. Can you put an inline spark tester on and see if its missing spark when it misfires? How about a noid light on the injector? Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 16, 2015 Share Posted September 16, 2015 maybe a valve is tight? right on the edge? vacuum gauge might show it. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.