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Hello Everyone,

I will try to summarize this as concisely as I can, but try to give any history that may be relevant. I have a 2012 Base Model 4WD Rav4 with about 40K miles on it.

Many months to a year ago I had a problem where the vehicle would shake/shudder sometimes at start time sometimes when I'm idling or going slow. It felt like the vehicle would shut off but it never actually did shut off. To me, the vehicle also took a bit longer to start than it used to after I turned the key. The dealer told me to change spark plugs which I did but I don't think it made a difference. Because the problem was intermittent it was hard to say if the spark plugs helped or if they were just changed at a time it was not happening often.

After the problem still reappeared, the dealer told me I had to clean my throttle body and they charged me for a cleaning. I also sprayed my mass air flow sensor myself which seemed to help a bit, too. The dealer did a terrible job of cleaning, but I also managed to get a mechanic to do a house call and clean the throttle body which was visibly very dirty.

Unbelievably, my dealer also forgot to replace the air intake filter, but I notice the RAV4 has a permanent filter which seems to be a good backup so hopefully no damage was done there.

I have changed my battery a few times over the past couple years and while it is under warranty and the battery people tell me it seems like I keep getting defective batteries, I have to wonder a bit.


I have installed a donnelly gentex auto-dimming mirror on my car (seems it went through fine), and I also was trying to troubleshoot some aftermarket fog lights and accidentally shorted the switch which caused some smoke underneath the dash by the steering wheel column. I had an electrician check it and they say they could not find any wiring or electrical problems and I probably just burnt the insulation off the fog light wires. Lastly, I also installed a 2.1A dual USB charger in one of my accessory slots. I don't think any of these made a difference, but I could be wrong so I am mentioning them.

This weekend I could not start my car and needed a jump so I went straight to the battery store. After changing my battery again, the guy who changed it said he gets a strange "NO OUTPUT" from the Charging Test which shows 12.97V on both "loaded" and "no load". He says he thinks that this means the alternator is failing because he would expect 13.3V at least. I am not sure if that is right (13.3V), but the main thing is that the battery voltage is 12.97V when the vehicle is off and when the vehicle is on it is still 12.97V.

Now that I supposedly have a new battery, the car sometimes shuts right off after starting or shudders like it will shut off. It does start after a few tries and revving the engine helps it to not shut off. I would say it happens less often at the first start of the morning than at the afternoon start when I go for lunch. Once its started, I do not notice anything strange while driving.

I am a technical guy that works with electronics but I definitely do not know much about cars or mechanic work aside from some theory, so I have a lot of respect for you experts and I would like to know what you think. I plan to take it back into the dealer for troubleshooting, but given the history I don't trust them much!

Thanks!
 

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1. Alternator failure or some connection with the smoke under the dash. Running voltage should be at least 13.3, 13.8-14 is better.

2. Buy a voltage monitor/usb charger for your 12V outlet.

3. Don't go back to that dealer.
 

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Discussion Starter #3
I really appreciate the quick reply! Thanks.

I am not sure I understand #2 though, are you saying get a voltage monitor so I can get real time voltage monitoring from inside rather than under the hood?

Are you also saying just get a USB charger that plugs in rather than trying to wire one?

Thanks!
 

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Yep, so you can monitor the voltage as you drive. I have several. The ones with a usb charger are the handiest.
 

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A battery voltage of 12.97 volts with the engine off sounds like voltage reading one would obtain just minutes after turning the engine off and no load applied. If this is the case, the reading has no value in diagnosing the problem.

The voltage measurement is only meaningful if the battery is under load. In other words measure the voltage with the engine off and the headlights or HVAC blower running. If the voltage is 12 volts (or higher) your battery is good.

The battery should read at least 13.8 volts when the engine is running, which would indicate the alternator is working properly.

Your voltage reading with the engine running already indicates a problem with the alternator, but since your problem is intermittent, I suggest you install the type of voltage monitor Dr. Dyno suggested so that you can catch the problem when it occurs, and try to determine a pattern when it occurs, for example in cold weather, hot engine, or on bumpy roads.

You may not have a defective alternator, but rather an electrical wiring problem that reduces alternator output.
 

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The 12.97V was right when the latest new battery was installed - probably about right for one just off a charger.
This comment, "I have changed my battery a few times over the past couple years and while it is under warranty and the battery people tell me it seems like I keep getting defective batteries, I have to wonder a bit." makes me suspicious that no proper diagnosis was ever done, just a bunch of unrelated money makers.
 

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Discussion Starter #7
An update:

Before taking my vehicle to the shop (I will do that tomorrow), I took my multi-meter and tested my voltage across the battery terminals when I started up this morning (started great with no shuddering, etc.)

I turned on my radio, my air conditioner, my auto-dimming mirror with compass, I turned on my headlights and my fog lights, and I even plugged a smartphone into my USB charger!

The drop in voltage was minimal and it stayed around 13.8V.

If the alternator was bad, could it perform at such a high efficiency sometimes, or does this point more toward a relay or a loose connection?
 

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While it's at 13.8V the alternator is working properly. (The usb charger takes less power than a light bulb.) Question is does it stay that way when you have your shake/shudder issues. It may be the infamous intermittent that neither you nor your dealer can diagnose until it's happening and why I recommend a way to monitor the voltage full time.
I've driven down the road with various gauges or lights taped to the windshield to find intermittent problems. Best of luck but from the sounds of it if it's the same dealer you mentioned they'll find some probably unrelated "service" to charge you for.
 
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While it's at 13.8V the alternator is working properly. (The usb charger takes less power than a light bulb.) Question is does it stay that way when you have your shake/shudder issues. It may be the infamous intermittent that neither you nor your dealer can diagnose until it's happening and why I recommend a way to monitor the voltage full time.
I've driven down the road with various gauges or lights taped to the windshield to find intermittent problems.

LOL, you being our "un-official" Dr. with a white lab coat and thick welder goggles getting out of that "Back to the Future" crazy-arse vehicle with all those items you mentioned when you test vehicles..... just need you to get out and say that famous "one-liner". WOW! Dr. i wanna now live on your street :lol:

 
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