I've got a '10 Max with 20K miles. It idles steadily at 650 RPM +/- 25 RPM when the AC is off, independent of any electrical draw items. With the AC on, it's 650 RPM +/- 150 RPM. Every minute or so, it'll fall to 500 RPM, the car will noticeably shudder, and then it'll pop back up to 750 RPMish. It seems to do this on a consistent time cycle. If I hold the throttle at 1500 RPM, the RPMs drop to 1000 or so repeatedly, but the car doesn't shudder or feel like it's about to stall.

Two questions:

1) Is this normal behavior? Does you RPM fluctuate to this extent, or at all, with the AC on?

2) Sight unseen, my local dealer proposed raising the car's idle. This strikes me as a band-aid on what various threads suggest is either a) a dirty intake manifold, throttle body, or intake air controller valve, b) a broken intake air controller, or c) and broken AC compressor clutch. Would I be correct in refusing this 'fix'? What consequence to raising the idle?

Thanks!

 

Two answers....

1.) I don't know the normal rage for the RPMs to go up n down with the AC on, but the fact is it does.. When i turn the ac on at idle it usually jumps like 100-150 rpms and tends to fall down though...

2.) I would not raise idling in my opinion.... first it will take more gas, secondly its going to run louder and more noisy....As long as your car doesn't die idling then i don't think u should have a problem...

 

Sounds like it may be the A/C Compressor kicking on... but not 100% on that though

 

My 2011 does this. I observed that when the compressor disengages the rpms will rise then fall, and when it engages falls then rises. This cycling only occurs when the cabin is cooled off (70-72 degrees in my car). I would say as long as the car is compensating for the load (coming and going) you're ok.

 

Do any of you experience shuddering? I don't remember this in the past, it feels like it's right on the cusp of stalling, and then it catches itself.

 

when I leave work I'll use my A/C and see if I get the shuddering

 

Mine does this when I have the A/C. Almost feels like the car is about to die. Guy at Nissan says that this is normal. It's the compressor shutting on and off

 

ive never watched my RPMs while it comes on, but I do feel a very slight shudder as it kicks on. I have a Stillen UD pulley installed as well so not sure how/if that would be affecting the AC condenser kicking on/off

 

I took the car into the dealer today. They're of the opinion the problem is just within the realm of normal. We tried another 2010. It had a more consistent idle and didn't shudder at all. They apparently checked the idle air flow and the manifold to little avail. In 3000 miles, I'm bringing it back for an oil change and they'll check the motor mounts, which are supposed to soften below 1000 RPM to reduce vibration. The only other alternative seems to be globally raising the idle 50 RPM, but that causes gas mileage to drop and may put undue stress on the transmission.

Thanks for the comments.

 

It may be possible that raising the RPMs by only 20 or 25 might make the situation more bearable, but not be enough of an increase to use much gas or cause excessive tranny wear.