RPM's dip while idling
 

Hey guys. My 2010 SV Premium has roughly 2000 miles on the car. Noticed something yesterday while sitting in the parking lot at work. I went to operate the windows, a saw a slight dip in RPMs while idling. When I am at idle, at about 600-700 rpms, engine dips about 50 rpms and comes back up. Thought perhaps I was going crazy, but I tried each window and the same happens with each of them. Tried it again this morning, same thing.

Anyone else notice this? Should I be worried?

Mine does the same thing, I think it's normal.

agree.

I imagine using the windows prompts increased output from the alternator, which the computer then compensates for by raising the rpms. Bet the same thing thing would happen if you turn on lights or AC while idling.

I agree. It has to do with when you draw power to certain devices.

Mine does the same thing. It's done it to all my cars I've had from what I can remember so I thinks it's normal.

it is normal nothing to worry about

I've seen headlights dim on some older cars, never seen (or should I say noticed) the idle drop significantly for electrical power drain...I'll have to check this afternoon. I could see all 4 windows at once maybe, but one window shouldn't be that noticeable...

Then again, I don't own a new car, and I have a grounding kit installed...:p

:sprint: Nothing to worry about.

every car with power windows does that..

Yeah, the electrical load is increasing on the alternator. It's normal, however, it's annoying.

I've noticed that the engine idles so low that when the AC compressor kicks on, the engine dips down to around 550 or slightly lower which causes a lot of vibration.

I've noticed in general that the Max has lots of vibration at idle.

I've manually bumped it up with my foot to 750-800 rpm and it's smooth as silk!

Except the control algorithyms in the Max don't react fast enough before the engine rpms decrease enough to cause a lot more vibration. I've found that even just sitting there idling in park with the AC compressor on constantly, the RPMS are lower than without the compressor on and the vibes are higher.


Anyone else notice that the wipers can rock the car when you are sitting still?

I'm not sure if the window motors are the same in the SV/Prem models as the rest. I did notice that the windows in my Max lower and raise a LOT faster than in the Altima the dealership had me in as a loaner.

umdpru. I don't even hear the RPMs dip let alone feel the car vibrate from almost stalling....That could indicate maybe a bad idle air valve or something along those lines if your RPMs are dipping that low while sitting still when using the A/C or other devices.

That seems like a massive fluctuation...shouldn't be that noticeable. You could see a slight dip maybe in the RPM's but not what you're describing...it shouldn't hold there either.

My last car was an 08 Altima until I bought the Max 5 months ago. I noticed the same thing! I was like, "Wow! Look how fast the windows roll up and down!" Haha

More expensive car...better window motors i guess lol

Oh, I tested mine last night just to be sure. When I only use one switch, the RPMs lower slightly. When I use all 4 at once, the RPMs dip just a lil more than with one switch.

Yeah the speed difference was amazing. I almost ashed my cigarette into the window of the loaner because i wasn't used to having to wait half a decade for the window to roll down heh.

Yeah a dip is normal, but the vibration he's describing from the RPMs dropping into stall range is not. That indicates that either the car is not sensing the drop in RPMs and compensating, or it is attempting to compensate and something mechanical is not working correctly such as the idle air valve.

The additional load on the engine is indeed calling a "stall-saver" routine into play. It's not just a sudden heavy electrical drain that causes this to happen - so does putting the transmission into gear from the neutral or park position, and so will steering the car when stopped with the engine idling even if the steering is entirely hydraulic assist.

This feature is even part of the better aftermarket EFI systems and has been for at least 15 years that I know of directly.

RPMs dropping way down suggests that something is out of spec / out of calibration, even though the A/C load has both electrical and mechanical components. There's probably a Nissan spec buried somewhere in their design documentation.


Norm

I just returned from my car dealer and had two issues addressed, 1) the variable idling (<500-600> rpm) and roughness as well as 2) the TSB reprogramming for the transmission due to slight vibration/humming with certain conditions. Overall the car runs much much smoother and is quite a bit more responsive. For the idling the fix was to reset the idle computer/setting and relearn it back to factory spec. Regarding the transmission I would recommend everyone to have it done as it is definitely worth it.

Rick,

I ran across your post here and was wondering....is there a TSB number that you need to reference if you take it in to the dealer for these adjustments? Any cost to me if I'm out of warranty? I've noticed that my RPMs drop each time the A/C compressor engages and you can actually feel the additional load when it does is in the seat and the steering wheel. I don't remember it doing that when it was newer (I have 41K on my 09' now).

Thanks !
Robert

yup yup yup..

Mine does it too

This happens on my 2011 even with 9K on the clock. Pretty much any car I've ever driven drops the RPM's a bit when the A/C compressor engages.

Does it do it quite a bit more severely at certain times than other times?