Wavering Idle and Dropping Voltage
 

I've been having a weird problem over the last few weeks. First off, there have been a few times where the idle wavers. Both times that it has been really noticeable, the oil temp was around 220, which isn't out of line to the best of my knowledge... I was driving fast, but not abusing the car. I pulled up to a drive-through, and while in park, I noticed the idle wasn't staying constant. It would go back and forth between 700 and 900 rpm, switching every second or so, almost like someone was tapping the accelerator in rhythm. This was only in park... if I kept it in gear with the brakes on, it stays constant at around 600 rpm. I was due for a 3 month service, so I went ahead and had them look at it... of course, they found nothing (they never do lol).

Anyways, that was over the weekend. I don't know if this is related, but starting yesterday, when I come to a complete stop (not in park, but just using the brakes), I often notice the voltmeter dropping from 14V to 13V. It only happens for about a second after I come to a stop, then it goes back to 14V. This has never happened before yesterday.

Does anyone know if these two are related, and what it might be?

Alternator-turn on your head lites, after dark, watch to see if they fluctuate , dash lights should do the same!

Kind of sounds like the voltage regulator is having issues.

It's going in for another look on Saturday.

Watching closely to the thread... Im experiencing the same problem with the voltmeter... 13-14... 14-13....

Have you checked your factory battery lately? The 370Z does not come with a maintenance-free battery.

This I didn't know. Any reason why they gave us that from the factory?

Most likely: cost savings.

Nice to see Nissan cheaping out. Bet a Mazda comes with a grade A battery

I'm hard on Nissan, when they are truly too cheap, but a battery, and what you get for your money regarding a 370Z, is not a bad trade-off. Most owners have a brand preference with batteries these days anyway, as they do their selection of gasoline and oil brands. Just spark-up a conversion on Optima batteries and you'll find the love 'em / hate 'em crowd in short order.

Perhaps the core of our batteries are forged from the infamous Miata door then?

One in the same.

Yeah, I check it at least every other time I fill up the tank.

So, I took it in again and the head mechanic said it's nothing to worry about, that it was probably always happening and I just never noticed it. He said that the battery is 12V, and the alternator adds the voltage on top of that. He said it is normal for the voltage to fluctuate between 13-14V when the car needs a little more electrical power. He said that the engine idles a little higher now and then to give the alternator some extra juice.

He did say that it is a problem if it goes lower than 13V; usually, mine only drops to about 13.5V.

Any comments on his verdict?

Ok, so I'm going to already say that I have no idea how to check this type of battery. I've never had one that required maintenance. I popped the hood last night to check it out, and I assume that we can't check the levels by looking at the side of the battery (I felt like I could do this if I took the battery out of the car, otherwise too much stuff in the way). So my question is...how do you read the 2nd part of this diagram? When I unscrewed a couple of the caps, I noticed some water in there, but how do I know if its enough? How can I tell if it is "full"? On the 2nd part of that diagram is the view looking down into it or are they showing us what it would look like from the side?

Help!