I have a 02 Neon, when I pull up to a red light or stop sign the idle gets real rough. If I put it into neutral the idle goes back to normal. I tried to do some searching on line and the top thing I found was the timing belt, but I'm not throwing any codes. I also read somewhere that getting the trans reprogrammed can help too.
Can anyone offer some help.

 

Check your engine mounts... Timing belt is not related at all.

 

Next time you stop and the idle drops to 200 RPM (so it seems), try turning the steering wheel about 1/4 turn in either direction. If the idle returns to "normal" then you have what's called idle undershoot.
Apparently it's part of the programming for the car to reduce fuel usage at idle when there isn't a need for a "higher RPM" idle. When you turned the steering wheel you increased the load on the engine and the PCM returned it to the higher idle setting.

If you find a fix for this, let the dodge guys know. They have not fixed this for the 11 years I've owned mine. I have had my idle so low I got low voltage codes from several sensors and had to disconnect the battery for 5 minutes to clear the codes and make the check engine light go out.
I give the wheel a 1/4 turn and go about my business.

Joe

 

200RPM? I don't know of an engine that'll run at that speed. 500-ish is generally pushing it. Neon engines generally idle around 600RPM.

 

Note my disclaimer: "so it seems".
Mine does not have a tachometer so it's a best guess. can tell you with confidence it's close to stalling and the lights get dim at night even though have a newer battery. If don't intervene, will get low voltage codes from the sensors.
Joe

 

I don't have a tach either, just knowledge from being on the forums long enough. It's 600 or 650RPM (proper).

 

Thanks, I will try these things.

 

I have a very similar issue with 2005 neon 2.0 SXT but the rough idle is more like a stutter that usually doesn't happen until I'm stopped at the light for 10-15 seconds. The stutter can be very intermittent and lasts only a few "stutters" sometimes and sometimes the engine stumbles for a few seconds (tach barely wiggles around 600rpm) and smooths out for a few sec. then stumbles again, ect.. Loading up the motor, ie A/C, lights ect. generally makes the condition worse. This also happens intermittently during acceleration. Once I reach cruising speed engine purrs like a little kitten, when in park also very smooth. I have cleaned throttle body, replaced Idle Air control valve and TPS, I also looked at vacuum hoses and everything looks good (visually). I was going to try the plugs next, but thought maybe someone has seen similar issues. I'm hesitant to think undershoot is the problem because my idle is steady around 600 with some stumbles in there when at lights or stopped and in gear. Any help is appreciated.

 

May want to clean or replace the PCV valve. On the 05 its located on the top of the valve cover, this valve is the exhaust return from the engine connected to your vacuum system, it is an integral part of your engines performance. It gets gummed up after a while. It is a very cheap part, and 30 sec to replace or easy to clean. Here's a link to good page talking about it.
http://www.aa1car.com/library/pcv.htm

I'm trying this tomorrow.

 

Sounds like you need to take a look at your spark plugs.