Hello fellow Mopar fans,
I have quite the problem on my hands with my 04 Neon. I don't know how to explain it but only it seems to idle rough at times. Sometime when it is in park but always when it is in gear. Like Drive and Reverse. It feels like a flutter in the engine. Like the car is going to stall. But it doesn't. I have also noticed that my fuel mileage is also starting to go down. Way down, we're talking 11 to 14 mpg. I know it gets better gas mileage than that. I have replaced the ignition coil, the idle air mixture, and throttle position sensor. I have also ran two different types of fuel system cleaner through the engine, Sea-Foam and Rislone. So far nothing has fixed the problem. Is this a common problem? I haven't seen or heard of anyone having this problem. I can't think of anything else to replace that effects the idle speed. It seem to drop to low. If it had a carb I would say it was the choke but I doesn't get better when the car warms up and it is hit or miss. One day it works okay and 15 minutes later it seems like it wants to stall. Once I hit the gas it is all go, no problems. The problem is only at an idle. Should I take it to a shop and let them look at it? Is there something I am missing? I hope someone out there knows what I am talking about and can give some advice on how to fix it. Any advice would be greatly needed.

 

On my 05 it was the idle air valve, it's on the rt side of the motor as your looking at it. I took my of and cleened it with carb cleener but this only worked for a few days.
https://shop.advanceautoparts.com/c3...G%2BQvDg%3D%3D

 

If its beyond the simple tune up... Your going to need a scan tool to fix it. Might check over on IDent-A-Fix and if the problem is common?