Maji

Wondering if anyone can explain what could be the issue.

While driving, the RPM dropped below 1k when off the throttle, and the dip in RPM caused the engine to stall. Luckily I was only going 20, so I could get to the side. It starts no problem, just that happens once in a while.
Now a few weeks ago, I had our Engine Light appear (Diagnostic coded Cooler Thermostat), and I haven't got that replaced yet. Could THAT thermostat be the cause of the RPM drop?

I appreciate any FB you can post.
Thanks!

Nuke

I doubt that the CEL is related to the stall. I'd do a few basic tasks to resolve the stall issue before any major replacements or dealer trips:

1. Replace the fuel filter
2. Clean the TB
3. Clean the MAF
4. Run 1 or 2 tanks of fuel treated with SeaFoam or Techron (in your case, I'd try the SeaFoam which is my choice when there's an issue as opposed to a simple, time based fuel system cleaning)

Normal idle speed is somewhere in the 550-650 RPM range. Check the OM.