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03 2.5x
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11 Posts
Discussion Starter #1
So long story short... CEL came on, P0304. changed wires and plugs. noticed oil in spark plug tube. changed valve cover gasket kit (spark plug shaft grommets etc.)..... reset light, back on within 200 miles.

next i changed injector loctations. i swapped #2 and #4. reset light. came back on within 100 miles. read P0304.

the missfire seems to occur at idle and below 2500rpm. some times it misses under moderate throttle below or around 3000rpm

have not checked compression or coil pack yet. could this be a timing belt issue? fuel filter? i have read just about every thread about this that i could find.

the car has right at 91000 miles , i have owned it since around 79000 miles.
it is an 03x manual tranny.

any input would be greatly apprieciated
thanks
j
 

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03 2.5x
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11 Posts
Discussion Starter #3
Checked the gap of the first set(replaced again after valve gasket job) plugs are Ngk copper, gapped from factory.

How do I go about checking the resistance of the coil pack, what should the reading be?

Thanks
 

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03 2.5x
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11 Posts
Discussion Starter #5
0304 still there

so i checked valve clearances. they are within spec. misted coilpack. no arking. ran a bottle of bg44k cleaner thru, a little better but still misfiring.
any more ideas?

thanks
 

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04 Forester X, MT
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1,039 Posts
sounds like you have done things in a good order. i'm not sure how much the coil is but if less than $75-$100 I would just try replacing that next, even though it seemed OK. they don't have a reputation for lasting forever.

as they don't have distributors I guess the ECU controls the firing. if the coil doesn't fix it i guess that would be next?!

of course the ECU gets signals from the cam and crank position sensors. i think it would take both of those sensors going bad to cause a driveability problem, but they should set a code different than misfire.
 

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03 2.5x
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11 Posts
Discussion Starter #8
im using some cheap duralast wires, but they are as nice as what was on there, and i have swapped them all around... i think i have elemenated that possibility.. i think

not sure if the timing belt is right. not exactly sure what to look for. i read that if the knock sensor goes bad that it could advance or retard the timing enough to miss.? is that right?

going to try and clean the knock, cam pos. sensor, and crank pos. sensor and re-install them. any ideas for cleaning?

as far as the coil, the problem really is most noticable on a cold start. as the enging warms up say after a 20min drive, it idles much smoother...but still missfires. ugh

thanks.
 

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03 2.5x
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11 Posts
Discussion Starter #10
Just a note, my friends car had this issue and it turned out to be a side effect of his headgasket failing.
eww... not something i want to think about. how many miles were on his car when the head gaskets blew?

did he have any other symptoms?

talked to a guy at the dealership shop the other day, he asked me if the spark plug in that cylinder looked like it was steam cleaned. i guess he was thinking the same thing(head gasket). my plugs have normal looking wear.
 
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