86subaru Posted February 4, 2012 Share Posted February 4, 2012 check engine light on , code says po304, , changed fuel filter, coil pk, gas cap, still on , flashes 8 -9 times stays on, starts fine , but when i push down on gas pedal sounds almost like ready to back fire ? any help thanks Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 4, 2012 Share Posted February 4, 2012 Well, that's cylinder #4 misfire, common causes of it on only a single cylinder are the plug, the plug wire, oil in the spark plug hole, or sometimes valve adjustments. Gas cap would have nothing to do with that code. Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 4, 2012 Author Share Posted February 4, 2012 ok, newer ngk wires/ plugs , 6,000 mi ago Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 4, 2012 Share Posted February 4, 2012 What some people do is swap two of the plug wires, like take a wire from a non misfiring cylinder, and swap that with the one on the misfiring cylinder (at both ends, plug and coil), then see if the misfire follows the wire. If so the wire is likely faulty. Also that year likes to get oil in the spark plug tubes, if there is a lot of oil in there that wasn't cleaned out when the plugs were replaced, that could cause it. Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 4, 2012 Author Share Posted February 4, 2012 yes good thinking easy , thanks Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 8, 2012 Author Share Posted February 8, 2012 still having problem, Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 8, 2012 Share Posted February 8, 2012 So when you swapped the wires around, do you mean the misfire stayed with the plug wire? Or did it stay on the same cylinder? Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 9, 2012 Author Share Posted February 9, 2012 same cylinder Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 9, 2012 Share Posted February 9, 2012 Hm how many miles are on? Has the valve clearance ever been checked/adjusted? If not one or more valves on that cylinder might not have any slack and be on the verge of not closing all the way. How's the power in general? If it's feeling sluggish/rough, timing could be off a tooth. Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 12, 2012 Author Share Posted February 12, 2012 changing the wires did nothing, alot of oil inside plug wires, power is very slugish , 3and 4 cylinder misifire , check engine light on flashes 8 to 9 times , if you slowly press gas pedal it is ok, mpg is less now, wouls changing the plugs help or not, 129,000 mi on her, Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted February 12, 2012 Share Posted February 12, 2012 i hear that oil in the plug tubes can cause mis-fires. oil in the tubes means the tube seals are bad. which also means the valve cover gaskets are probably bad. (why replace the VC gasket without replacing the tube seals.?) 3 & 4 share the same half of the coil. but it could also be the igniter supplying the coil, since the coil is new. there is a test but i don't know what it is . Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 12, 2012 Author Share Posted February 12, 2012 ok, are the seals hard to change, Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 13, 2012 Author Share Posted February 13, 2012 changed both plugs with ngk, , found cylinder 4 plug covered with oil , Quote Link to comment Share on other sites More sharing options...
unibrook Posted February 13, 2012 Share Posted February 13, 2012 Does misfire only happen when car is warm? If so, has the front oxygen sensor ever been replaced? If not, do that next. Quote Link to comment Share on other sites More sharing options...
MilesFox Posted February 13, 2012 Share Posted February 13, 2012 Have you checked the knock sensor? when it goes bad, it retards the timing under load and causes a power drop, which in turn causes the transmission to hunt around for gear. Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 15, 2012 Author Share Posted February 15, 2012 no but will check , changed pvc , fuel filter, plugs, wires, no real change misfire 3and 4 Quote Link to comment Share on other sites More sharing options...
Robert Harik Posted February 15, 2012 Share Posted February 15, 2012 Can try swapping injectors, valve clearances, compression check. Quote Link to comment Share on other sites More sharing options...
86subaru Posted February 16, 2012 Author Share Posted February 16, 2012 ok, thanks, may just take to my mechanic Quote Link to comment Share on other sites More sharing options...
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