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!

Unsrew the cover (there are three for each terminal). Get a tiny flashlight and point it towards the water. There are some straight lines below the surface of the water. There are two metal "prongs" (for lack of a better word) which should be touching the water; if there is enough water, the lines will "bend" in the area around them. If the lines look straight, you need to add DISTILLED water; I use a medicine dropper.

Just make sure you top the battery up with Nissan Ester Water.

:bowrofl: Rep pint & point for that pup!

Did you try what I posted, post #2?

It is normal to see some fluctuation in the voltmeter depending on the condition of he battery and the loads on the system. Typically 13.0 to 14.5 is a normal range. Though low voltage indicates a non charging symptom ie alternator or regulator problem and over charging sytem can cause more problems. Over charging of more than 15-16 volts can blow out lights and fry computors leading to expensive repairs. In addition to checking the level of the fluid I would recommend checking the specific gravity of the battery acid with a hydrometer found at any local auto parts store. This is a better indicator of battery health. Water has a specific Gravity (SG) of 1.000 in a Sulfuric Acid battery A SG of 1.265 is ideal and it can be slightly higher or lower in each cell but if you have one or more cells showing close to 1.000 indicates a dead or shorted cell it's time to replace the battery. Also since you have a wavering idle that in itself may be causing your voltage to drop. Your alternator puts out very little charge if any at idle. Dropping below that rpm may cause a significant drop in charging voltage. You may not have anything wrong with the charging, but have an idle conrol issue. Just a little advice from a prior F/A 18 Avionics Tech Hope this helps you guys out.

Yeah, nothing like that. I think I was over-reacting to normal behavior that I had just never noticed.

Thanks! I used to have a hydrometer for my saltwater aquarium... wish I'd kept it.

Guys,
Try this. Go to your MFA sensor. Turn your car off, unplug the MFA sensor. you will get check engine. plug the MFA sensor agine, and use any OBDII and erase the fault code. It will be fixed. I just figured it by luck.
One more thing, when your idle goes to 13's use the wiper, does the idle goes agine to 14's. mine does, that how i figured it.
good luck.

I started having a weird issue today and wondering if it's the same as this issue...I was city driving all day in Hollywood and it's just crazy stop and go traffic. Normal ~190 oil temp. I have an '09 manual. When I come to a complete stop or car was in neutral, 7 times out of 10 I would say, idle would drop, car would shake a bit, then idle would go back to normal, after a few times of this happening I started to notice that every time it would happen the Voltage would drop and I'd always catch it on its way back to 14 as idle goes back to normal.

I was guessing voltage drop is due to car almost shutting off because of low idle/shake then when idle goes back to normal so does voltage but I don't know why the idle is acting weird? Could this have anything to do with my "recent" exhaust install/tune (or lack thereof)? Or is this pretty much exact same issue OP was experiencing and I should just check my battery and not worry about it?

Thanks as always for any input guys :tiphat:

I had this same problem and in my case a new battery was the fix. After 52,000 miles and 3.5 years the crappy stock battery was done. The car would seem like it was going to stall out when stopping at an intersection. I read this thread and discovered about the maintenance Required battery. After adding 1 1/2 cups of distilled water to get my battery back to level, the idling problem was much better, but I could still see the volts fluctuating. I had the battery tested and it was done. I have a new Optima battery now and all is good.

Good to know, thanks :tup:

Battery voltage drop along with idle only at idle
 

I've had my 'Z' for 11 years, I'm a avionics technician in the aviation business for 37 years. For those who do not know what a avionics technician is, I work on all of the electrical and navigation system of an aircraft. Battery voltage on my 2009 "Z" never fluctuated "NOT EVEN A TWICH", in 11 years. it stayed at 14.4 volts no matter what you turned on in the car. My problem started when my battery crapped out on march 2020, a week later the alternator went out and like I have never done before went to an auto parts store and replaced with one of there's. The battery voltage and idle drop started soon after. Returned the alternator to the auto parts store got another one, no joy. Returned the battery and got another one again no joy and problem persists. Purchased a brand new alternator from Nissan $650 dollars later no joy. Replaced battery with brand new high output gel battery $450 dollars later and still no joy. so for those that think its a battery, alternator, and yes by the way I did purchase two new MAS sensor from Nissan and still nothing. Its none of the above. The battery voltage drop should be so slight when operating normal that you will never even notice it ever. There aren't enough system draw in a car to overcome a 120 amp alternator. I have contacted Nissan and they are mute about this issue. If someone comes up with a fix please advise.

Same issue on my 2014... but it really cost me.

So it started doing the idle drop thing, but I thought that was because the transmission had been replaced and I honestly just decided since going through that whole process I'm not going back to a nissan dealer unless its an issue that prevents me from driving.

So one day on the way home from work, got food, got back in the car, and had this horrendous smell. Turns out my RF amp and sub both self destructed. I'd noticed lower voltage than normal on and off over the preceding few weeks, but it would go back to above 14v most of the time.

After the amp/sub both self destructed, and letting the car sit and air out from the fumes produced, the car wouldn't even start. It only sat for two days.

Got the 6 year old battery replaced and all has been perfect since then.

Moral: If you have an older battery and run a few subs, even professionally installed, there's an added risk. Better to get the battery replaced ahead of time or tested as soon as any symptoms show up... As much as RF says if in an under current or voltage scenario the amp will self protect, that's wonderful except in cases where it doesn't do it fast enough and destroys the sub.

So I was out:

a new battery
new amp <--- luckily I Have a new RF amp, a much bigger one sitting on standby
new sub <---- will likely just have a custom box done for the spare tire area since there are a lot of thugs/wanna be thugs in phoenix.


So: Don't be like me!! get the battery checked and replaced ahead of time, so this way you save yourself from other possible related issues. Mine had zero issues starting up each day, the only real symptom was as others have mentioned, the rolling into a complete stop and subsequent RPM drop.

This is the FIRST time in 30 years of aftermarket car stereo use I've ever had an amp or sub go bad on me, and had both installed professionally, and both are reputable brands: RF amp, JL 10w3 sub. Clipping is a killer, and so is my boneheaded move to not just get the battery replaced sooner as preventative maint.

Wow... now that's a nightmare!!

Any updates?

I'm now looking at toyota/lexus products...

fluctuating voltage at idle only
 

https://www.youtube.com/watch?v=vYtyDX9RTWs

My 2009 370Z after the alternator crapped out, I have replaced it twice and battery twice. The problem persisted, after doing some research it turns out that the PCM (Power Control Module) gets confused about where the throttle valve positioning should be. Also the PCM controls the alternator and tell it when to and not to charge the battery. Most of the computers on the Z have capacitors, they store energy to keep the processors energized with small amounts of energy so they do not loose their memory. I searched YOUTUBE and found this video on how to give your Z and many other cars an enema. Accomplishing this video to the letter fixed my Z. The link above takes you directly the the video. Once you accomplish this and restart your car all the computers reset themselves and you will see the voltage drop and come back up at least once if not twice while the car re-calibrates itself. If by chance the link does not work the title to the video is : How To Reboot Your Car ~ Battery VooDoo.

The issue is permanently fixed and voltage steady as a rock at 14.5 like it was for the last 10 years. I did place a response and if you cannot find it follow this video to the letter.

https://www.youtube.com/watch?v=vYtyDX9RTWs

Like I stated on my response the battery voltage my swing back onc or twice while the car re-calibrates itself.

Or you could take one of the battery terminals loose and step on the brake pedal for a few seconds. Will work with any car that has functioning stop lights when the car is turned off (ie, all of them).

There IS a good reason to take the negative terminal off first - if your wrench shorts to ground, you won't have a dead short. Once the neg is loose, shorting the positive to ground won't hurt.

Putting a dead short (the jumper in the video) across charged capacitors is a bad idea. The rapid discharge can damage capacitors and other elements inside the ECM. Most are rugged enough to handle it but why take the chance? If you use the jumper-wire method, put a resistor in series.

Nice job on finding that. :tup:

Voltage drop with idle drop at idle only
 

As I had previously posted, I thought my problems where over when I discharged all the car capacitors. Wrong it cam back shortly after that, again the idle and the battery voltage fluctuating at idle. I found the true fix for this and you probably are going to think I'm nuts but here we go. When I replaced my original alternator that fried itself I followed the installation procedures in the manual under CHG (charging) in that section it tell you to go to EM (engine mechanical) to check tension. This is by checking the tensioner and making sure that it is between the lines as shown in EM-13. Here is where the fun begins, I found that my belt was at the last line which indicated it should be replaced. I had just replaced the belt 40k ago, then in EM-13 it says tension adjustment refer to : EM-139 DRIVE BELT. Wonderful, I go to that page and it states no adjustment needed self tensioning. I started my t/shooting again. I removed the serpentine belt. I found that the alternator stay item 6 on CHG-24 has the hole that attaches to the engine side elongated. It's not plug and play, I wedge a piece of wood between the alternator and the engine to force the alternator as far out as it could go. Then I torqued all the bolts, installed the serpentine belt and behold the tension was perfect in between the limits indicated by "B" on EM-13. I started the car and behold all perfect just like before my battery and alternator crapped out. No where does it tell you about the alternator stay adjustment. Now I do not know if a bushing or sleeve may have fallen out of my stay but from the pictures I have seen there are none. At idle the belt is hardly touching the pulley even with the tensioner in place. Its been a two weeks since I did this and all ok. So I loosened up the alternator stay and retorqued it without taking up the slack and the car started acting up again. So at least in my case I have confirmed the cause of my problems.3 batteries 3 alternators, 2 mass air flow sensors and numerous hours later it is fixed. Hope this helps some of you.

[IMG]http://www.the370z.com/members/javie...-tensioner.jpg[/IMG]


http://www.the370z.com/members/javie...nator-stay.jpg

http://www.the370z.com/members/javie...-tensioner.jpg

Hello everyone!

Could GREATLY use help on this.

So as my above post mentions, I had the stock battery last for around 6 years / 60k miles. One day all of a sudden my bass amp (RF) just self destructed, and so did one of my JL Audio 10w3's. So bad, that the entire interior smelled like an electrical melt down! Pulled Sub box, and stopped using amp.

A month later, the stock battery would not start the car without a jump start. Took to dealership, had battery replaced. Everything was FINE.

Until about 2.5 weeks ago I stopped driving the car every day, and would let it sit in the garage for 2-3 days. Then one day it wouldn't start without a jump start. Then 2 days later, car starts on it's own just fine. Then a day after that, completely DEAD. Not a single light on the dash, nothing works at all. My tiny taclife jumpstart battery failed to work even after charging it to the max.

So called the insurance company, tow truck dude shows up with a giant jump start battery type (the blue one with the handle). Car turns over slowly and finally started after about 3-4 seconds.

Drive car straight to dealer - dealers tests battery and shows me a receipt tape like print out stating the battery they put in there 4 months ago is just fine.

Since then, I've been just disconnecting the negative terminal if I need to let the car sit for more than a few hours as I'm now working from home like everyone else.

One thing I've noticed, which is similar to others posts: the voltage meter.

Recently at stop lights, I notice the voltage drop to one tick below 14, and then if I'm driving for quite a while at 80+mph on the freeway, then it will slowly go back above to 14.1-3ish. In the past 6+ years of ownership, that battery voltage thing barely moved, and now it's moving around consistently, especially at stop lights. I've also had that strange idle rise/fall only once at a single stop light.

Other facts: 72,000 miles on the car now, serpentine belt has never been changed, stock alternator, battery replaced 4 months ago, and I did relocate to phoenix (hot as an oven) in January - The heat here kills just about everything, and I'm told by many that it's not uncommon to only get 18-24 months out of a typical battery. I did finally completely remove the dead RF amp that may have been doing some type of parasitic draw, but it does not seemed to have changed any behavior of the volt meter. Other than that, I'm running a 5 year old pioneer deck going to a 4 channel RF amp that was installed at a stereo shop. I did check to see if the amp that is working shuts off, and it does.

I'm open to suggestions on where to look next, and I may simply have to start with cheapest stuff first: serpentine belt ? (mine is about dead center per the diagram below)

Please advise if anyone has any ideas.

Well finally got a SES or " Service Engine Soon " light... will have to buy code reader and go from there.

Was hoping some people could chime in with ideas before the stealership tries to BK me! Will post again with update :stirthepot:

Can you scan for the DTC?

That's the plan, still looking at scanners on amazon at this point...

** ordered charging system tester and 3-in-1 tester/code reader/multi-meter; Figure whynot have both and have some redundancy. **

Well... not really sure what to say now...aka: dog chasing tail!

P0603 So this must be just from leaving the battery disconnected a few days which is what I've been doing out of fear that I have some parasitic draw or god knows what at this point.

As stated above, it wouldn't start after 3 days of sitting with avg temps in the 110-120 degree range outside (car is garaged).

Tester says the charging system: battery, starter draw, alternator are fine...

Here's my plan: Leave battery connected, test it each day, and go from there.

Bumping this back up. I've noticed my car didn't start after a week of no activity. The battery was about 9 months old, but I went to the shop and they recharged it. It then started up fine. It's been fine for a few weeks but just noticed that my voltage fluctuates from 12V to the normal 14.5V or whatever. I've never seen it dip that low. I noticed even while driving, it goes from 12 to 14, then stays at the normal 14.

Is my alternator going? Not charging the battery consistently? That doesn't seem quite correct either.... Thoughts?