Here's a pic of the tach on my "new" 1999 Outback wagon,warmed up and sitting at a stop in Drive with the brake on.
It has a recently swapped dohc 2.5L. With the swap it got new plugs and air filter. Plug wires look pretty new, as does the fuel filter.
If I put it in neutral or park, I don't notice any significant change in rpm's up or down. If I turn the AC on, it goes up "maybe" a hundred rpm.
The rpm's don't fluctuate at idle.
When it's idling as shown, it's rougher than I'd like (quite a bit rougher than my '92 Legacy 2.2).
It feels a bit rough under acceleration too, although it doesn't seem to stumble and gets up to speed ok.
Even though it feels like it's idling too low, it's never died when idling so far...
In searching, I see that it's not possible to manually adjust the idle higher, so if this is too low, what can I do to raise it.
BTW, my '92 Legacy idles around 800 as does my '95 Nissan.
Is this too low for a warm idle? What should it be?