My car normally is 11,000 rpm at idle in park.
6,000 rpm at idle in drive but with the brake pressed.

Now when I start it, the needle goes to about 11,000 rpm then slowly within 10 seconds goes down to 6,000 rpm. This is in park at idle. I can also hear the engine sound dying down and getting really quiet. I'm worried the needle might just keep going and I'll have a dead car.

Drive idle is still the same.

What's going on?? Pulled 0505 code (no problems)

 

I'm hoping you are off by a factor of 10 in the above post, i.e. by 11000 you really meant 1100 and by 6000 you really meant 600.... the maxima tach doesn't go to 11,000

Assuming the above is true, your idle is fine.. (maybe a tad low) but nothing to worry about... when the car starts, it idles higher (1000-1200 rpm) until it warms, up, once warm, idle in park should be anywhere from 550-700... (depending on if the A/C is on, and whether or not you have a stick or auto).

Cheers,
Nirav

 

Thank you, and yes my mistake with the zeros.

I always have the system on pretty loud and today when I turned everything off and restarted, I could hear the engine sound dying with the rpm decreasing and it freaked me out!