I just recently purchased this 2004 sebring 2.4l 4cyl that has been sitting up for about a year. The previous owner didn't have any more interest in it when it started idling rough. I replaced the plugs with the ngk model and the old plugs were gapped at different spaces. It's still idling rough with no code. I've had autozone hook it up to their scanner and still no code. Is there anything I'm overlooking. I've changed the plugs wires and distributor but can't seem to get the shake out of it. It drives good but red lights are a nightmare. It shakes badly and on some occasions has turned off. But restated immediately after. I love this car and want to get it in tip top shape. Any advice??

 

Rough idle can be many things. Since it sounds like you eliminated an ignition problem I would suspect either dirty or bad fuel injectors or a vacuum leak; either a hose or a leaking intake manifold. Do a visual inspection of all vacuum lines. I would also try a can of fuel injector cleaner and see if it helps.

John

 

I have the same issue on an 06. I got an OBD reader and noticed that the IAT is reading as high as 130F when the temp outside is 75F. Not sure if that has any correlation though. Everything else on the OBD reader looks fine. I tried a trick I saw online though about spraying break fluid around the manifold and watching the fuel STFT and it did mess with it which indicates a vacuum leak, so I ordered a new gasket set which should be in today. I'll let you know how that goes... Crazy thing is if you floor it it runs really freaking well actually, but at idle it feels like I'm riding on old diesel tractor haha

 

Note mine is the 2.7L though