I have a 2005 dodge SX (Neon) 2.0 litre, 4 cyl, auto. it has shaking and vibrations while in idle, when I get up to higher speed it isn't as bad. When the car is in Drive Gear and I am stopped at a light, the idle drops down to almost 500 rmp, the car acts like its on the verge of dying, lots of vibration/shaking with it. I have replaced the plugs, coil pack, cleaned all the fuel injectors. When I start the car up and it is running, I get interference in the engine when I disconnect the injector connector on cylinders 1, 3, and 4. Not on 2. I have even put a different injector in cyl 2 and still no interference when I disconnect it. I have cleaned all the injectors. The engine acts like nothing happened on cyl 2. All the other cylinders the engine bogs down a bit and then auto adjusts when I disconnect the fuel injector.

I took a multimeter to the connectors on the fuel injection connections, while the car is running, I get a full 13 volts on cyl 2, when I connect the tester to the positive and negative connectors. When I do the same test on cyl 3 and 4 I get only 1 volt; however, on the the ones with 1 volt reading, when I leave the positive tester terminal in the fuel injector connector and put the negative side of the tester on the cars ground, I get a full 12-13 volt reading. Is that normal? When I reverse it on the negative side of the connector for cyl 3 and 4 only showing 1 volt, and put the negative lead up in the connector and the positive to the batter, still no 12 volt. Could this mean a grounding problem?

Plus the new plugs I put in, are all fawled up with black residue, not direct motor oil, but more like a black residue. I cleaned the plugs, checked their gap again, and put them back in, I even reversed the plugs for cyl 2 with 4, vise-versa, still misfire on cyl 2. When I pull up on the spark plug connector while car is running I can hear the sparks plugs firing on all 4 cylinders.

When I pull the spark plug rubber insulators up from inside the motor, there is no oil visible. Cyl 2 though has a brown rusty look inside towards the bottom.

I have checked for vacuum leaks, none. I checked the air filter, it wasn't too bad. I also replaced the PVC valve.

 

Having the exact same thing going on plus code 0304. Lost

 

It was the computer failing that caused the misfire. Ended up going to a wrecker, getting a used brain, then had a mechanic program it to the fob and all. The used computer set me back about $100, and the programing about $150.00.. I hope that helps.