It takes about 3/4 hour to perform the update, IIRC.

 

That's a long time, I guess 100$ doesn't seem that bad for that then,
..but I don't want to do it if my car is already up to date, sucks they don't tell you.

Maybe we already have the update and without it, it would
get worse when we turn the AC ON like darthroush.
So maybe the update would only change rpm when A/C is ON.

 

They can tell you before they do the work; that's the thing.

For the 2000 Neons, there is a driveability improvement TSB, but it doesn't describe any of those problems.

There is TSB 18-017-01 REV A. It is for 2000-2001 Neons and has to do with engine roughness, and it does mention the A/C. This TSB update apparently includes the update in the above driveability improvement TSB.

 

I also have the same exact problem. I would like to think that an update flash of the pcm would fix the problem and if any yall do let me know. More than likely the front pump on the tranny is worn and the line pressure is dropping too low at idle. that is why when you put the car in neutral it gets better and also why it doesn't seem as bad when the car is cold. when you turn on the ac, turn the wheels or the heater the pcm ups the idle to compensate for the additional load hence upping the line pressure. when the line pressure drops too low the clutches in the tranny start to bind. I hope I am wrong and will be exhausting all other possibilities first. getting really frustrated with this car and the more i research these cars the more depressed i get.again if anyone gets the updated pcm flash and it works, drop me a shout. I DON'T WANA PULL THIS TRANNY.....

 

I have had to replace the transmission oil pump on my car. Does the same thing it did before.

 

i have a 2000 neon and i trouble shoot the idle cause i have the same problem 2000-01 neons have a kickdown band on the transmission and its in the routine maintenance every 30,000 miles or two yrs. its called the automatic transaxle band ajustment and the kickdown band is like downshifting on manual trans so i would try that you can get specs online or buy a chiltons manual its always the small stuff people over look hope it helps and let me know if it does

 

And every once and a while take off the breather tube open the throttle plate and clean the ridge of carbon that forms behind it (closes of the little air gap that allows proper idle air into the motor, The IAC has to try and overcomensate for this).

and if you use your defroster in the winter the clutch on the A/C will cycle bringing the revs up (so your low buck no diagnosis fix WILL work for you in the winter) LOL

 

Just did the kickdown band adjustment as suggested. Read that in Chilton's manual & simply followed the directions. Quite easy actually. But the problem still remains though.