I just bought my first Neon about 3 weeks ago. It is a 03 SE with auto with 99k. A lot of miles for a 03. I have a rough idle. No codes so I threw plugs, wires & air filter at it since I did not know the last time they were done. My rough idle is still there. I was going to clean the throttle body & IAC valve this weekend. Any other suggestions? Thanks.

 

mine has a somewhat rough idle also... perhaps a neon thing?? lol how rough of an idle are we talkin?

 

its probably a vaccuum leak. check for that, start at the intake mani and work your way from there

 

mine idles well just every once in awhile it gets a slight bump to it

 

I think Spikey Mikey is onto something: I have a 2000 Neon with a 2.0 and a three-speed automatic trans.The engineloses HP at load, either uphill, on the highway; or during hard accelleration. AC affects this, too. I found good fuel delivery (45PSI at full volume), and good compression, -but low vacuum at idle, around 15 inches with the AC on (at idle) and 18 with the AC off. [checking at the PCV valve line, with the PCV valve disconnected] I can watch the vacuum gauge move up and down as I turn the AC on and off. I checked the timing and belt and put a new belt on, though it didn't need one and replaced the plugs but it did not help. I can't run this car up a any kind of grade without downshifting. Is there a drawing of the vacuum system to look at, or is there some commen areas for leaks to occur?-Any ideas, friends?