I have a 2017 86 and I would not say its ever had a "rough" idle. On a cold start before it reaches operating temp, I get a small shake every once in a while, but the rpms do not drop and there is not any sound associated with the shake. When I say shake I mean 1 at a time. It reminds me of what it feels like when a car passes by when you are stopped at a red light and the air turbulence causes your car to feel like it is nudged by the air. It is very, very subtle though. Once it is warmed up, you would barely be able to tell it's running if you could not hear the direct injection (HPFP and injectors).

Mine is a little rough when it first starts, but once warm, I have no issues.

Some observations:
- On start the car idles at a higher than normal level, this continues for a minute or two, and once warm the idle drops.
- If I let the car start rolling out of my parking spot (in neutral, while warming up) the idle will drop as soon as I start moving. Seems like there is a sensor.
- I try to warm the car up for at least a minute or two every morning, drives much better warm, at least in my opinion.

Sorry to hear about this, my car has been rock solid since I got it (knocks on wood).

No way to say this without sounding condescending (even though I am not trying to be) but here I go anyway:
Is this your first ca ever? Every car made since they invented the automatic choke starts at high idle an drops once warm enough or you move it.

high and steady at first, then drops around 40 seconds in, then stable and slowly goes down until hits about 600rpm..

My FRS 15 idles rough sometimes, I think it depends on where I get my gas... but I haven't really plotted it yet. I was told at the dealership they can flash my car with an update? I think I might do it soon.

Does a vibrating shifter knob indicate a rough idle? It seems like more often than not, lately, mine will be slightly vibrating, and then I grab it and notice, yeah, this thing is shaking a bit.

Thanks for the replies, and I'll know to be very specific next time. Going to see if the dealer has one I can sit in at idle to compare. I'll let you know if mine is "normal" or not.

I had a 13 FRS and just bought an 86 a month ago

The FRS would idle high at warm up and the drop to 5-600 and idle fine, except for the crickets but they never really bothered me much.

The 86 idles high at warm up and drops to 5-600 after that. So far no crickets :)

The only difference I have noticed at warm up is the 86 seems to idle higher for longer than the FRS did

Oil pressure on a hot engine at idle (750) is only 3 to 5 psi. That's scarry low. So I had my tuner (Shawn Church) raise the idle to 950 so now my idle oil pressure stays at 20 psi when hot. Car idles smooth except when the AC is on. Then rpm goes up and down as AC compressor comes on and off. Also being supercharged that adds some more draw off the engine. But all in all can't complain a bit.

2013 BRZ...idle is smooth all the time, even before it warms up. Driven in temps from 98 to 10 degrees. Only idle issue is that with fast stops it will dip a few RPMs and then recover

Drove motorcycles for 20+ years, all weather. Was a way of life.
Now I am older and wanted a car that was sort of like a bike: not too convenient, more fun than most to drive. But with heating. And windows. Got this.

So its all good, I am many things: husband, small business owner, computer guy. Nobody that knows me would say I was a car guy.

I do love my FRS though, and I have been learning a lot including from you and this forum. So thanks!

That makes sense. Just really took me by surprise that somebody would not be familiar with the concept of high idle on a car.

Man, you got exactly the right first car to be coming from nothing but bikes. Respect.

There's always that one guy. Pretty awesome.

My 2014 UK spec GT86 idles fine most of the time.

The AC compressor clicking in and out raises and lowers the idle by about 100rpm. Sometimes clutch drag causes it to hunt, falter, recover, repeat. Shifting into neutral sorts it immediately.

However occasionally, like for 2 or 3 weeks every year the idle routinely falters when the AC compressor clicks off. Revs drop below 500, car shakes and it recovers. Then 10 seconds later the compressor kicks in and out again and it falters again. After it's little spell for a few weeks it returns to normal.