Hello, I have a 97 dodge neon with the 2.0 sohc engine with aprox. 128k miles. What is happening is when the engine is cold and I go out to start it, once it starts up it runs quite rough at idle, the check engine light comes on and usually starts to flash which is bad, after the vehicle gets to operating temperature the flashing goes away and it turns to a solid light and the rough idle goes away slightly. I notice that if I rev the RPM's up and hold them at about 2k when the car is warming up the check engine light goes solid and stops flashing. When driving the car, it runs faily well, it doesn't choke out or anything. The engine itself isn't making any bad noises, it isn't overheating either. I checked the oil and coolant, they both look good, but the exhaust smells like fuel. I just replaced the coil, spark plugs, wires and air filter all with brand new parts. I also did a valve cover gasket along with the valve seals. I thought that replacing these things would fix the problem but it didn't seem to help at all. The p0304 code was there before I replaced all those things, as well as afterwards. It is the only code I am getting though and from my assumption that code means that the cylinder 4 is misfiring. I am not sure where to look next. It just puzzles me that it runs really bad when it's cold and just o.k. when its warmed up. Any advice would be greatly appreciated. Thanks in advance.

 

Try swapping fuel injectors and see if the misfire follows the injector. You may have a stuck or plugged #4 injector. Also, try cleaning the fuel rail out.

 

Thanks das, i did pull the injectors and cleaned them as well as the fuel rail. I swapped number 1 with number 4, but it is still running bad. This thing is so frustrating. Could the head gasket be leaking? I checked the oil/anti freeze and nothing is mixing together. The temperature never goes above the half way mark either. I just wish I could get it running halfway decent so I can drive it this winter!

 

But did the code change to P0301 instead of P0304? If so, then it would be your injector. Also, check for a leaking intake manifold gasket around the #4 cylinder. They can leak and draw in more air throwing a misfire code.