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Old 09-20-2012, 07:10 PM   #1
redrex2002
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Default misfire code help please

hey guys, where do i begin...
i own 2002 wrx that i bought in 2005 with 42k miles on the clock. it now has 202k miles and i just recently gave it a fresh coat of paint. while doing the paint job and waiting for my mechanic buddy to put in some power steering lines the car sat around for about a month, only being started briefly to move it around the parking lot and the shop. i got my car back last night and started driving it around town running errands. i was able to drive maybe 5 or 6 miles before my cel started flashing at me. so i scanned the code and it was a p0304. so i had the car towed back to the shop today and i swapped out the coilpacks and the spark plug.

when i go to start the car and see if all is well it starts perfectly and runs normal for the first 30 or 45 seconds, then the motor starts to shake and run rough. then the check engine light begins to flash again and i shut it off.

i am at a loss for what to do next and rather frustrated. over this last summer i have put 800 dollars of paint and clear, as well as a starter (x4), cps sensor (x2), battery, spark plugs (x4), and one coilpack for cyl. #3 all to try and pix a p0335 cel that as still to this day eluded capture. i have all but run out of money at this moment, right now me and my wife are sharing one car which is getting almost impossible now that school has started.

please help me save my car, if anyone has any ideas as far as what i should look into next i would really appreciate it.

and now banna's
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Old 09-20-2012, 07:58 PM   #2
pghana66
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have u had the timing belt serviced?
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Old 09-20-2012, 08:40 PM   #3
redrex2002
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yes at around 120k
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Old 09-20-2012, 08:54 PM   #4
GGSimpreza
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There are a ton of threads, search P0304. This misfire code can be everything from needing plugs replaced, to your motor having ringland issues.

Start diagnosing with the easy stuff, plugs and wires, moving them to different cylinders and check lights.

Best thing to do is a compression/leakdown test if you have the equipment. It's pretty cheap to get done.

You can search a ton, but there are so many causes you need to get your car looked at professionally if you don't have experience working on cars.


Quote:
Originally Posted by pghana66 View Post
have u had the timing belt serviced?
How would this be the first thing you ask about for a misfire?


Also, P0304 is a cylinder 4 misfire, not 3.
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Old 09-20-2012, 10:45 PM   #5
pghana66
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Quote:
Originally Posted by GGSimpreza

How would this be the first thing you ask about for a misfire?
was looking at the other code in the thread saw cps was maintenaced, car starts but then goes awkward. 200k, figured id ask as didnt see it in the listed updates.
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Old 09-20-2012, 11:23 PM   #6
redrex2002
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my mechanic said i should try and find out where the pcm is located, he said i might have a bad ground somewhere in there because we have eliminated the plugs coilpacks and wires unless there is a broken wire somewhere in the harness.

on a side note does anyone know if the engine wiring harness from a 2004 wrx will swap into my 2002 wrx?
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Old 09-20-2012, 11:55 PM   #7
nomoredsm
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i strongly suggest a compression check and if good then a leakdown test.. My 02 wrx acted similarly when piston #4 had a cracked ringland. I changed plugs, swapped coilpacks, cleaned grounds, cleaned maf, but rather than waste $ i just swapped the coilpacks to see if the miss went from cyl 4 to another and when it didnt i did a hot compression check to find only 90psi in cyl 4. Also, if cyl 4 is missing then you will most likely wipe out rod bearings in cyl 2, i did.. Its a horrible feeling to find that a rebuild is whats needed, so have some ginger ale handy to calm that sick stomach!!
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Old 09-21-2012, 12:14 AM   #8
TwoFifty
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The best place you can start with a misfire in my opinion is this,

Swap plug from cyl 4 to different cylinder, see if misfire follows

Swap coil from cyl 4 to different cylinder, see if misfire follows

Swap injector from cyl 4 to different cylinder, see if misfire follows.

If code follows part then you know where the problem lies.

If not could be an internal engine issue, Perform Compression test and leakdown test!

In fact you can perform a compression test while you've got that plug out to move it, might save you a little time depending on the results.
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Old 09-21-2012, 04:56 PM   #9
redrex2002
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thanks guys i am not shure that it is an internal problem. because when i start it up it takes 30 seconds to a minuet for the light to start flashing. then if i clear the code while it is running it runs fine for annother min. then the light starts blinking again. i would think that if a valve is sticking or a ringland was cracked then it would start flashing as soon as i started the car and would return immediatly after being cleared while it was running
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Old 09-22-2012, 01:13 AM   #10
laxton
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I HAD THE EXACT SAME PROBLEM! Changed coil packs and plugs and cleaned mafs.. Still nothing. Done a comp test and it was 80psi! Put in a scope and seen bad valves so I got all new ones. When the head was removed I descovered I has multiple cracks in my head. (explanes why it runs fine when cold) its bc the cracks were small but as it heated up the cracks would expand and I would lose more compression. Please take my advice and get a test ran to save u more time.
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Old 09-22-2012, 10:30 AM   #11
redrex2002
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thanks i definitely will. i have access to a totaled 2004 wrx is there anything stopping me from swapping that motor and harness into my car?
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Old 09-22-2012, 12:43 PM   #12
Haelan
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Quote:
Originally Posted by redrex2002 View Post
thanks i definitely will. i have access to a totaled 2004 wrx is there anything stopping me from swapping that motor and harness into my car?
Why not do a compression test on cylinder #4 first? You'll know in 10 minutes whether there is a major problem or not.
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Old 09-23-2012, 01:03 PM   #13
nomoredsm
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Quote:
Originally Posted by Haelan View Post
Why not do a compression test on cylinder #4 first? You'll know in 10 minutes whether there is a major problem or not.
You can lead a horse to water, but cannot make him drink
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Old 09-23-2012, 01:23 PM   #14
redrex2002
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i am going to have my mechanic do a compression test but my car is at work right now and i do not have access to it untill monday. i am obviously going to perform all the tests and check before i get involved in a motor swap i was just making sure that if it does come down to a bad head or piston etc. that i can use a motor from a 2004 wrx with half the miles that my car has and was running up untill a week or so ago when my friend rear ended a dump trunk lol bad for him great for me potentially
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Old 09-24-2012, 10:31 AM   #15
frostmasta
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I had same issue, turns out the timing belt had slipped 1 tooth off.
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Old 09-24-2012, 01:41 PM   #16
redrex2002
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if the timing belt was mis-aligned wouldent both cyl. number 2 and 4 be having problems? annother thing to dbl. check i guess thanks guys. i am trying everything i can to save my baby. just got to wait for my mechanic to have time to get it in and start running down the list of possible problems
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Old 10-01-2012, 03:18 PM   #17
redrex2002
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ok i finally had time to do the compression test today. the results were

cyl. 1, 135 psi
cyl. 2, 142 psi
cyl. 3, 132 psi
cyl. 4, 148 psi

it seams that the motor and its internals are A-OK, especially for the amount of miles that i have on her. lol i guess running 4 quarts of mobil 1 full syn. and a quart of lucas really does do the trick lol.

any more ideas of where to look next. wensday probable i am going to JB weld a peice of scrap metal over the flex section of my downpipe because i have a really big exhaust leak commin from there. hopefully that helps but i am still open to any other things to check out.

and thanks for all the help so far guys.
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Old 10-01-2012, 06:46 PM   #18
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Old 10-01-2012, 08:05 PM   #19
Kastley85891
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My fix was as simple as a loose negative battery terminal
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Old 10-15-2012, 01:29 PM   #20
redrex2002
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hey guys finally got my misfire problem figured out last friday. finally got around to swapping the fuel injectors around and sure enough the misfire went from #4 to #2, so out came all 4 injectors and i shipped em all out to deatschwerks saturday. hopefully ill get em back thursday and i can have my baby up and running by the weekend. damn it feels good to finallyhave this problem figured out it only took me a month and a half to find the time lol
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Old 10-15-2012, 03:50 PM   #21
CanadianImprezaSTi
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Glad to hear you solved it without a rebuild!

Quote:
Originally Posted by laxton View Post
I HAD THE EXACT SAME PROBLEM! Changed coil packs and plugs and cleaned mafs.. Still nothing. Done a comp test and it was 80psi! Put in a scope and seen bad valves so I got all new ones. When the head was removed I descovered I has multiple cracks in my head. (explanes why it runs fine when cold) its bc the cracks were small but as it heated up the cracks would expand and I would lose more compression. Please take my advice and get a test ran to save u more time.
Sorry to drift off topic, but since metal expands under heat wouldn't it close the cracks as it got hotter?

Not to mention, small cracks in the heads of a WRX are fairly common.

I'd say your valves were the only issue.

Joel
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Old 10-15-2012, 07:57 PM   #22
danger1138
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Damm. I love good endings!! Gives me hope in regards to po304 code on my hybrid setup. Though i doubt its a piston problem in mines but u never know.
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