Misfire Cylinder 4 Code P0304

[Lefty2053]

I have changed out the Plug,Wire and the Coil pack. Still have misfire. Any ideas? Friend told me it could be the start of a head gasket going. Said it is just dripping down the cylinder that causes the misfire.

 

[Turdle]

I have changed out the Plug,Wire and the Coil pack. Still have misfire. Any ideas? Friend told me it could be the start of a head gasket going. Said it is just dripping down the cylinder that causes the misfire.

Could be-but I would check the compression on bank 1. It's easy, just screw the gauge into the spark plug hole and crank the engine until the gauge jumps 3-4 times.

Do each cylinder (1-4) and write down the readings. If they are within 10% or so of each other than I would suspect the fuel injector on cylinder 4. You might make sure it is plugged in good by reseating the connector. ( pulling it off and plugging it back in)


Are you loosing coolant without a drip to find?

If not, it would make me suspect that injector even more.

edit. pull the fuel pump relay and disconnect the coil packs when cranking for compression test. You don't want the engine to start or cylinders to flood with fuel. --lol

 

[Lefty2053]

Thanks for the help. I will have that done if I can't figure it out soon. I remember using gas from a certain station and had the same sputtering on low RPMS and it turned out to be the fuel clogging my injectors on a Chevy S-10 I had. I have been using fuel from that same station again(years later) and I am hoping it is the fuel I get from them. On the Chevy I changed gas stations and never had the problem again. I'll try that first and if it doesn't fix it I will have someone test compression.

On a side note. 1 and 1/2 years ago I was going ice fishing. The truck had a bad miss and not being close to the internet I limped the Explorer home. Turned out it was the spark plug wire broke off and of course it was cylinder #4 . I had all the plugs and wires replaced then. Could limping the truck home on 7 cylinders have messed up #4 ? This was 1 1/4 hour drive home.

 

[rlgdguy]

I've done the same things (plugs, wires, coil) and am getting the same fault code along with the random engine misfire code. I have been experiencing a little fluid loss without any drips and was wondering what was going on. Sounds like I'm in trouble here. I faied my state emissions because of the code (reset twice, but comes back almost instantly and engine light pops on) and really don't have a lot of money to fix this. What do you guys think I'm looking at here?

 

[rasouth]

I had the same problem on my 4.0. Changed plugs, wires, compression check... It turned out that I did not have a couple of my wires clipped into the little brackets that go around behind the valve cover. I guess it was shorting out. Re-ran wires and no more misfire.

 

[rlgdguy]

Tried that, no difference. Next thing to try is an injector?

 

[rasouth]

A compression check is a quick and easy way to figure out what could be wrong. If your compression is 130 to 150, you are okay, meaning you probably do not have a cracked head or blown gasket. If compression is low, 80s to 110ish, could be a coolant leak into cylinder causing misfire, or a crack between valves. Check spark plug. If it is wet and smells like gas then maybe no spark, maybe injector.