I think the fast idle 07 G35S 6MT is a bit high. I just had a cat back exhaust and tune so maybe it
was always this high, but it's just louder now. Starts at 2300 and within a minute comes down to
1200 or so and then ends up where it should be when fully warm (around 700). I did an idle air
relearn but no change.

Please let me know if there is anything I can do to troubleshoot. Thanks.

 

Is this from a cold start, like after it's sat turned off for 3+ hours ? If so, it's normal.

 

Yes - cold start. Thanks for the info. Must just be louder now with the new exhaust.

 

When you did the idle air reset did you make sure to do it on a hot engine, with everything that consumes power turned OFF, including the air conditioning and radio, vehicle in park or neutral. It's possible to either miscalibrated it because it wasn't at the right point to actually do the test, or have it not accept the relearn condition because of other factors.

The idle will have immediately dropped and relearned if it ACTUALLY worked.

Hot engine rpm should be 650 +/- 50, cold engine rpm is irrelevant, the engine will do what it needs to do. You can check actual rpm with an OBD2 scanner which is a lot more accurate than the low end of the factory tach.

 

The part I bolded is the key. What's odd is there are soooo many posts about "my car idles really fast when it's cold" (no offense to folks, I get that many are learning). What's concerning is some people respond "that's not right" or "it shouldn't do that" and I have to wonder if their car doesn't idle fast when cold.

The OP did indicate his idle when warm is 700 so personally, I think everything is okay with his car.

 

Yes - warm idle is within spec (see photo). My only concern was noticing the loud cold idle since
I had the exhaust/intake/tune done. Wanted to make sure nothing got messed up. Thanks for
the responses; it must just be that my ears weren't adjusted to the louder exhaust, and thought
maybe the idle had gone up.

 

Cold idle sound (regardless of rpm) does sound different than hot idle, you're probably just noticing it now that it's louder.