2000 Plymouth Neon idles at low RPMs in warm weather and feels like its going to stall. Why?

2000 Plymouth Neon. Just had it in this shop for this on-going problem, but nothing seems to fix it. When it's warm outside and the car is warmed up, in drive and in idle, the RPMs (which normally are at 800 or so when the car is cold or the weather is cold) drops down to 590-610 and the car begins to shake, but not stall.



I can make this go away by giving it gas, putting the transmission in neutral, or in park.



The car drives well. It just recently had spark plugs and wires changed, motor and transaxle mounts replaced, oil change, etc. etc.



It feels like the car is running too lean, but I can't figure out why this is only happening while at idle in drive and only on warm days.



Any ideas what this is and how to fix it?2000 Plymouth Neon idles at low RPMs in warm weather and feels like its going to stall. Why?
try cleaning the IAC valve

cost: free

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