AC compressor hard engage

[dell30rb]

The AC compressor on my 08 4.0L pathfinder makes a little more racket when it engages than I think it should. You can really feel it hit and the motor makes more vibrations as it feels like it is not running smoothly due to having a load at low RPM.

I haven't used the AC much - is this something the computer will eventually learn and get accustomed to? On some of my other vehicles I can tell the computer opens the idle air control a bit immediately prior to AC compressor engagement.

Thanks

In possibly related news the engine makes a little more noise when under throttle than I would expect it to. It runs fine just not the silky smooth I would expect. (I'm picky about these things). I have 70k on it and will probably start with a throttle body cleaning, run some injector cleaner through it and maybe replace the spark plugs, though the manual says they are not due for another 30k miles.

[disallow]

I would do a check on your idlers and the bearing in the AC compressor.

[dell30rb]

I might have to check that...

I get (very) quiet birds chirping from the belt/pulleys for a few minutes after a start on a cold morning, but it goes away when warmer or if the temp is above 50 degrees. Haven't tracked it down yet

[skinny2]

These aren't the quietest or smoothest engines in general....but they put out a lot of power for their size. I recently changed my drive belt and tensioner and the morning chirping is gone.

I notice it when my AC turns on...but I don't think it's abrupt. You might have a compressor bearing on the way out as mentioned. So far might is doing a fine job with 90k miles.

[ShipFixer]

The compressors make a noticeable warbling noise when the bearings start to go. I replaced mine once because it got pretty bad; the brand new one was silent, although it's starting to warble a little bit again.

Sounds annoyingly like the beginnings of the cam chain tensioner too...

Aside from that, the engine particularly when cold does run a little rougher at idle when the compressor comes on. This is a big V-6 at low RPM with a sudden load, only so much you can do to accomodate that in design. It's pretty smooth for what it is. Premium gas does seem to smooth out higher RPM's on mine but it's not like I've measured it with accelerometers.

The intake induction noise on this truck is fairly loud. You can always add damping and insulation to the hood to absorb some of it...

[smj999smj]

I might have to check that...

I get (very) quiet birds chirping from the belt/pulleys for a few minutes after a start on a cold morning, but it goes away when warmer or if the temp is above 50 degrees. Haven't tracked it down yet

There was a Nissan TSB for this issue. It instructs to replace the serpentine belt and tensioner with the countermeasure parts listed on the bulletin.