Rought Idle at red lights

[skyvo]

Hey Folks, hoping someone could help point me in the right direction here:

2016 Nissan Versa SV with 65,000 miles. Always maintained according to service manual/intervals, mostly at dealerships. Replaced Serpentine belt at 50,000 miles due to cracking and flushed CVT fluid at 60,000, otherwise just regular oil changes/tires/filters using only Nissan OEM parts.

About a month ago, I started noticing that the car would rough idle at red lights (CVT in Drive, brake pedal depressed) with RPMs dropping to 575. I performed an Idle Air Volume Release but this did nothing. I scanned the car with BlueDriver (OBD2 tool) but pulled 0 codes. The weather hasn't been too cold either, generally around 50F - 60F degrees.

Steps to reproduce:
1. Start Engine and drive around for 10 minutes to warm everything up then return to garage. With engine continuing to run:
2. Disable all load (lights, radio, AC, defrost, etc.)
3. Engage Parking Brake
4. Shift into Drive
5. Depress Brake Pedal (Doesn't have to be all the way down, around 50% of the way is enough to trigger this issue).
6. Observe the following data points:

a. RPMs immediately drop from 675 down to 575
b. Mass Air Flow Rate between 1.93 g/s - 2.1 g/s
c. Battery Voltage between 14.0v - 14.4v
d. Relative Throttle position is shown at 2.4%
e. Squealing/Squeaking noise coming from Serpentine Belt area (seems to be close to the ground but not sure exactly which pulley/component might be causing the noise).

At point #6, adding certain loads will either make the problem go away or make it worse:
- With windows all rolled up, pull all 4 window switches up (as if to close them) - observe RPMs drop further down to 560 and idle gets more rough and squealing get a bit louder. Release after a few seconds to not burn out the switch.
- Turn Blower Fan selector from 0 to 1 and engage AC (depress "AC" button and confirm AC light is on) - observe RPMs immediately rise up to 675, squealing/squeaking and rough idle goes away right as the compressor clutch engages. Depress "AC" button and confirm AC light goes off and observe RPMs again drop down to 575 and rough idle/squealing observed again.

At this point I've been given different stories from different mechanics so posting here to see if anyone had any similar experiences?

[VStar650CL]

First thing to do is make sure there are no vacuum leaks. Your scanner can tell you that. If the STFT is high at idle but drops and stabilizes above 2K RPM or so, there's a leak. If a leak is indicated and you don't find anything external, try a new PCV Valve. If there are no leaks, next thing to try is cleaning the MAF and Throttle Body and then redoing the IAVL. Take a MAF reading at something above idle before the cleaning, then again after IAVL at about the same RPM. If you see a change of more than about 8% before and after, carbon in the TB was probably your issue.

[skyvo]

First thing to do is make sure there are no vacuum leaks. Your scanner can tell you that. If the STFT is high at idle but drops and stabilizes above 2K RPM or so, there's a leak. If a leak is indicated and you don't find anything external, try a new PCV Valve. If there are no leaks, next thing to try is cleaning the MAF and Throttle Body and then redoing the IAVL. Take a MAF reading at something above idle before the cleaning, then again after IAVL at about the same RPM. If you see a change of more than about 8% before and after, carbon in the TB was probably your issue.

Thank you so much for the quick feedback!! Just to close the loop:

I went with the process of low hanging fruit:
1. Looked around and listened for a leak but could not hear/see any signs of one. Data confirmed there isn't one, or isn't a significant one at least.
2. Removed and shook PCV valve - heard clanking like a new valve so assumed this isn't an issue
3. Removed intake air hoses and cleaned throttle body. There was a lot of carbon buildup on the TB and this seems to have solved the issue!
4. Performed IAVL

Now the car runs totally fine and I can feel it having a lot more power. Thank you so much for the help!!!

[VStar650CL]