February 4, 201214 yr 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
February 4, 201214 yr 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.
February 4, 201214 yr 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.
February 8, 201214 yr 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?
February 9, 201214 yr 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.
February 12, 201214 yr Author 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,
February 12, 201214 yr 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 .
February 13, 201214 yr Author changed both plugs with ngk, , found cylinder 4 plug covered with oil ,
February 13, 201214 yr Does misfire only happen when car is warm? If so, has the front oxygen sensor ever been replaced? If not, do that next.
February 13, 201214 yr 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.
February 15, 201214 yr Author no but will check , changed pvc , fuel filter, plugs, wires, no real change misfire 3and 4
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