Code p 304, I have done spark plugs,wires,ignition coil, top motor mount. Car has been fine for a week then the engine light came on again with same code. Car runs fine, rpm are good.

20

Asked by Oct 29, 2015 at 08:20 PM

Question type: Maintenance & Repair

Car does shake when at a stop. Not
as bad before I fixed the motor
mount.

7 Answers

71,345

Cylinder # 4 is misfiring...

1 of 1 people found this helpful.
20

I know that I can't figure out what else to do. Replaced all the usual stuff. Car seems to run fine Could be a false light

1 of 1 people found this helpful.
71,345

The causes are: Bad spark plug, bad wire, bad ignition coil for that cylinder, dirty or bad injector, or bad compression.

1 of 1 people found this helpful.
67,365

Remove the spark plug from that cylinder and look at the tip. Sounds like the plug is fouling out. If it's wet and smells of gasoline it's probably a leaky fuel injector. If it's black and oily I'd suspect a weak valve guide seal or weak rings on that cylinder. Especially if this is an older model with some miles on it. Run a compression test on that cylinder. If it's lower than it should be (usually around 150 PSI is good) get a spark plug anti fouler. This is really a "Band-Aid" but will cure the problem for awhile. HTH. -Jim

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20

Plug was dry, not wet or black and oily. Car seems to run fine. Has a little knock when cold and shakes a little when at a stop

1 of 1 people found this helpful.
67,365

What's the compression reading on the cylinder? What kind of car is this? -Jim

71,345

Compression or anything to do with the spark is all I can come up with.

1 of 1 people found this helpful.

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