I have a 2010 g37xs and when it's on its A game it's the best car I've ever driven but god help you if a butterfly in China flaps it's wings too hard cuz it's gonna act up and there might not be a solution. Mine started getting po420/430 codes and had no power after like 20 mins on the road so 3 shops told me clogged cats. Cost? 3000 bucks.....nahhh. put on test pipes and it's way better but it still kinda losing power here and there and the idle fluctuates slightly. At night the lights kinda flutter. Tested the battery and alternator and they are good. Looking online this loss of power issue is insanely common with no common answer. Last thing I did was clean my maf sensors. Seemed to help a little bit but might just be me lying to myself. It's not limp mode cuz I can redline it in manual mode but it's definitely sluggish at times. Any ideas guys?

 

Who tested the alternator and how was it tested? Specifically, did they test the ripple? Also, does this "flickering" vary with engine RPM's?

 

It only does it at random times mostly when first started at idle as the rpm needle fluctuates. I did all the relearn stuff. I think he tested the alternator with a scan tool. Ac being full blast or off makes no difference. When I first got the car it shifted at 2500 rpm but after fixing an intake leak and chopping the cats off it shifts way better around 3-4k and not as jerky. It's an annoying issue to run like a dream then lose like 1/3rd of your power at the next stop sign. Also don't help that this accelerator pedal is very stiff and unlike most cars I've had.

 

In other words the alternator was load tested and likely not tested for excessive ripple.

Alternators use what is called a "rectifier bridge" to convert the AC voltage generated into DC voltage which is used by the car. In AC voltage, the electrons alternate, or bounce around. This fluctuation is ripple. Any time your lights are flickering, especially on these cars, the rectifier is allowing excessive ripple (AC voltage) to pass through the diodes to the rest of the car. Being random in nature further points to the diode(s) slowly failing.

I would get a second opinion on the health of the alternator. Any ripple ≥0.5VAC (500mV) is considered bad.

Perhaps others will have some additional ideas.

 

If the idle is erratic, might want to have the throttle bodies and MAF sensors properly cleaned. Inspect the engine filters as well. Follow the correct relearn procedure for the idle. If the idle does not correct after all that and there are no DCT's related to it or other issues cussing it, boost the idle with Nissan Data Scan 3 or equivalent to set a solid idle.

And yes I agree, these cars are very finicky.

 

I think 0.0005 VAC is a typo... Did you mean 0.5 VAC?

This article gives some good tips:
https://automotivetechinfo.com/wp-co...-Diagnosis.pdf

 

Good catch, Sonic, thank you for catching that. I edited the post.