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.