need bb Posted April 20, 2020 Share Posted April 20, 2020 I was WOT passing a car and afterwards I noticed that something wasn't correct with my engine I pulled out btssm and confirmed that I had misfires in cylinder 4. I was surprised to see that the misfire counter was constantly increasing and soon after I received the P0304 check engine light My tune is set to enter limp mode with minimal knock and learning view was normal with proper fuel trims and an IAM of 1.0. The car is clearly not running on cylinder 4 as it vibrates a bit at idle and acceleration is labored. At this point I am thinking it is: Spark Plug/Coil PackInjectorCracked Piston I have already build the engine once with Cosworth Pistons, so I am hoping I don't have another cracked ringland. I was planning on having my local mechanic perform a compression/leakdown test as the next step. Thoughts? Link to comment Share on other sites More sharing options...
Pleides Posted April 20, 2020 Share Posted April 20, 2020 Valves out of adjustment? Bad MAF sensor? Bad O2 sensor? Lots of things could cause it. I've yet to see somebody with a bad coil pack on our turbo engines. My car has the original ones at 212K, 15 years old. Plugs, very well could be an issue. Built motors call for spark plugs every 25K, most of them. Link to comment Share on other sites More sharing options...
DaveWaters Posted April 20, 2020 Share Posted April 20, 2020 If you haven’t already, check your fpr vacuum reference hose for a leak as thats on the #4 intake runner. Link to comment Share on other sites More sharing options...
Tehnation Posted April 21, 2020 Share Posted April 21, 2020 easiest and quickest way to check if its spark plug, coil pack or injector is to just swap them with another cylinder and see if it follows, if it does then its a cheap fix. Coil packs do go bad on these cars, they wear out like any other part. I don't see a forged piston cracking, something else should go before aftermarket pistons. Link to comment Share on other sites More sharing options...
need bb Posted April 21, 2020 Author Share Posted April 21, 2020 Thanks for all the tips. I will have to try swapping the coils/injector and plugs. I don't think it is Bad MAF or Bad O2 sensor as the fuel trims are good and the other cylinders are running without any misfires. Engine has less than 30k miles and I am running way less power than the engine was designed for. The issue happened right after a few second WOT in 3rd and 4th gear, so engine was at max load. Only thing I can think is that injector 4 failed. Link to comment Share on other sites More sharing options...
Max Capacity Posted April 21, 2020 Share Posted April 21, 2020 Make sure the coil connector is tight, that was the fix for one of the other members a few years back. FWIW, when I changed my plugs, I did not remove the wire from the coil. On the wagon I was able to get all four coils off with the wires connected. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
need bb Posted April 23, 2020 Author Share Posted April 23, 2020 Make sure the coil connector is tight, that was the fix for one of the other members a few years back. FWIW, when I changed my plugs, I did not remove the wire from the coil. On the wagon I was able to get all four coils off with the wires connected. Wouldn't I want to also move the coil between cylinder 3 <-> 4 to validate the coil is good? Link to comment Share on other sites More sharing options...
NORULZleggy Posted April 23, 2020 Share Posted April 23, 2020 Make sure the coil connector is tight, that was the fix for one of the other members a few years back. FWIW, when I changed my plugs, I did not remove the wire from the coil. On the wagon I was able to get all four coils off with the wires connected. Do this and Also I had misfire on cylinder 4 on my WRX. I was running hard home from work and the car went limp going over a big bridge in my town. I got it home, and it came down to being a bad coil pack at 86k miles. On the car I know the coil packs get really hot due to how close they car to the heat of turbo and DP. I went ahead and ordered 4 new pack from Rockauto and never had it come back. (intermotor was the brand) very good product). I swaer they were subaru brand with no markings. Link to comment Share on other sites More sharing options...
Infosecdad Posted April 23, 2020 Share Posted April 23, 2020 Diamond Electric is the Subaru OEM, I'm not sure if Intermotor manufactures their own or resells someone elses. Link to comment Share on other sites More sharing options...
xt2005bonbon Posted April 23, 2020 Share Posted April 23, 2020 Wouldn't I want to also move the coil between cylinder 3 <-> 4 to validate the coil is good? between 2 and 4 (next to each other). see if misfire follows. If it does, problem solved. I also zip tie the coil pack plug to the coil pack. Link to comment Share on other sites More sharing options...
need bb Posted April 28, 2020 Author Share Posted April 28, 2020 Swapped coils and the misfired moved to cylinder 2. I have ordered a new OEM coil and hope that resolves the issue. More to follow. Thanks for the suggestions so far. Link to comment Share on other sites More sharing options...
need bb Posted May 6, 2020 Author Share Posted May 6, 2020 Got the new coil swapped in and everything is back to normal Link to comment Share on other sites More sharing options...
Stphnhrrng Posted December 30, 2020 Share Posted December 30, 2020 Valves out of adjustment? Bad MAF sensor? Bad O2 sensor? Lots of things could cause it. I've yet to see somebody with a bad coil pack on our turbo engines. My car has the original ones at 212K, 15 years old. Plugs, very well could be an issue. Built motors call for spark plugs every 25K, most of them. Wouldn’t the car also throw a code for an MAF or O2 sensor if they were bad? I keep getting a cylinder 3 misfire code ONLY on my 08 2.5l N/A legacy. changed plugs, changed coil pack, has new NGK wires. After the coil pack the CE light went away for a couple weeks but just came back today. not really sure what the next step is Link to comment Share on other sites More sharing options...
markc0220k Posted December 31, 2020 Share Posted December 31, 2020 (edited) Not sure if mine ans is correct, but i just simply clear the code. The point is, i knew i didn't engage the clutch well, almost die at a stop light then the cel pop up. 4~5yrs ago first time i had P0304, i took my car to a shop, they suggested to change the plugs and coil packs, plus few things (O2 sensors, waterpump and etc) i forgot. i know they were trying to steal my paycheck, but since it was about 80k so i did it. but then the same night the code pop up again due to i guess my bad clutch engaging (the idle was very low, i believed it was just because the battery has been disconnected, so the ecu reset and relearning?). anyway i called the shop next day and they said something nonsense to me, so i ignored them (because a week after i picked up my car from the shop, i turn on ac and i realised they mess it up, my freon was all gone! So i don't trust them anymore..) and clear the code myself. At the time i realised that every period of time i changed/disconnect the battery, ecu reset/relearn, thus idle went low, at the time i had bad clutch engage at stop light and thats cause the P0304 code! Since then i just simply clear it (yes, i changed battery few times, removed and charged it many times, then same ecu/low idle + bad clutching few times!). Mine is 120+k now. beside the CEL, i don't see anything wrong before and after clearing the code. hope this help Edited December 31, 2020 by markc0220k Link to comment Share on other sites More sharing options...
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