Code PO 304, running rough, light on

[upnorthdad]

Hi,
I got the code today on my 99 ranger and it is PO 304, cylinder #4 miss fire. Can you guys tell me what I should replace. I was going to start with plugs and plug wires....
Thanks dave

 

[97ranger4x4]

Yeh I would check your plugs/wires to start out with. Ohh and just replace it with motorcraft plugs. Thats a factory replacement. I believe they are gapped to .054 as well.

Do you mind giving some more info about the truck. How many miles? What other things you have done to it?

Has the truck been misfireing over a period of time, or just all of a sudden.

 

[upnorthdad]

more info. on truck

Hi,
Its a 1999 4x4 that has approx. 110,000 miles on it. I have not done to much to it maintenace wise in a while so yesterday I replaced the fuel filter, air filter and pcv valve. The problem is it's seems to idle a little rough.... when your going down the highway it almost runs o.k. but when you go up a hill you get real bad chugging.... if I downshift into 2nd (auto) it is better so I knew it couldn't be the fuel filter but it has been awhile since I changed it. I also read somewhere it could be the lower intake gasket, I sure hope its not that.....Oh yeh the light came on and stays when this happened.
Thanks Dave

 

[AngryLepercon]

It needs a tune up. I had the same problem. Replace wires and plugs. I had a cylinder #4 misfire and thats what fixed mine. A dropped cylinder will give you a rough idle but also check your air idler.

 

[jmg8550]

Yeh I would check your plugs/wires to start out with. Ohh and just replace it with motorcraft plugs. Thats a factory replacement. I believe they are gapped to .054 as well.

Do you mind giving some more info about the truck. How many miles? What other things you have done to it?

Has the truck been misfireing over a period of time, or just all of a sudden.

i used motorcraft plugs and they lasted about 25,000 miles. couldn't get new ones so i replaced them with NGK platinum plugs. truck never ran better. i usually use motorcraft and have had good luck with them also.