Yesterday I drove my 2009 Camry Hybrid back from work. I got to a traffic light, well after the usual warm-up time (the gauge was about centered). After I came to a complete stop, the car went to EV and immediately turned the ICE back on. It did this for about 3 times (shut-off / turn back on).
On the way home, I had the feeling that the car was harder to get into EV than normal.
The outside temp was 55degF.
In stop and go traffic I did often get to a complete stand and sometimes did cruise at very low speeds, but the engine wouldn't shut off. Instead the battery got charged to about 90% (more than normal, but hard to tell from the dash. I don't have the nav). Eventually I did turn off a couple of times.
Right now I am not very worried, but my mileage was a little worse than usual and I was wondering if someone here has some hints why it behaves like this.

BTW. I love this forum. I have been lurking around for a while now and I enjoyed reading and learning!

 

Looking at your location, it's a bit chilly up there. If your climate control is engaged at all, it is going to be pulling heat from the engine. It will need to turn on, sometimes on a short-cycle to keep the heat flowing to the cabin.

I wouldn't worry about it too much, absent any fault codes or warning lights.

 

Thanks McGyver. You are one of my favorite TV characters. I feel safer already
I had all the fans off. I always do this in cold weather to get the car to warm up quicker and I hadn't gotten around to turning it on yet.
I kept it off on the freeway too, when it didn't want to go EV and stubbornly kept charging the battery. I think it may be some software glitch that probably got reset when I turned it off at home.
BTW. we had 55 degrees yesterday (about 13 degC for Canadian and European visitors)

 

Andre,

Did you just fill up the tank? If yes, there are some things that might have caused it. Other than that, there are times that the system will do strange things. I just chalk it up to software gremlins and don't worry about it. Mine has almost 75,000 miles on it now but no major quirks at this point, just a good solid car.

 

Thanks David,

I have maybe 60 miles on the tank. I filled it up a few days ago.
I bought the car not too long ago with 47k miles on it (now over 50k), but I also took the extended full warranty with 0 deductible up to 100k, so I am not overly concerned. Consider me a technologically interested Hybrid enthusiast
BTW, what are those things that happen after fill up?

 

Several things can happen with gasoline. If you go a long time between tanks, you might have gone from a summer formulation to a winter formulation on the gas. The feds require the gas volatility to be increased during the winter for easier starting. This "lighter" gas has fewer BTU per unit than your summer blend.

The station might have gotten a load of gasoline with more than the normal percentage of ethanol. That will cause a re-calibration on the ECU which might have had an effect on your EV mode.

Another issue would be a load of bad gasoline. That could come from two main causes. The first would be an oxygenated fuel (ethanol added) that sat too long in the dealers tank. They have a tendency to separate and the ethanol will attract water faster than a cathouse can get a sailor.

The other would be just a contaminated tank due to outside leakage from rain water, ground water, etc.

 

could it be that the computer decided the battery needs to be balanced, fully charged and recalibrated? The car could be working in mysterious ways, but it doesn't have to be quirk or any type of gremlin. The underlying software is rather complicated and it could be doing things which we don't even know about. Even much older, non hybrid cars had for example learning period, where computer would collect data about driver's habits and set the car accordingly, so for the first few miles the car would drive differently, every time you disconnect battery for example. Unless there are error codes I wouldn't worry about it. As far as bad gas is concerned, It could explain lower mpg, but how would that explain engine running more often, instead of in EV mode? and if the engine runs more, the mpg could suffer even with "good" gas.

 

Pete,

The engine ECU can be recalibrating the engine due to bad/different gas for the reasons you just stated. If the engine is not running the same as before the ECU will vary the fuel trim, timing advance, injector pulse width, etc to keep the emissions in line. If the gas has minor amounts of water, the engine will have a few misfires that will be counted but will not set a code. They can be found in the live engine data however.

All of those can/will affect the engine run time. The battery condition, state of charge, temperature as well as the electrical load on the system and drive train demands all affect the way the system runs.

As already proven by the programming on the Prius, as much as this might come as a big surprise to you, programmers do screw up and leave bugs in software. A "gremlin" in the software is certainly possible as is a sensor not recording correctly or a hundred other possibilities in these complex cars.

 

GeorgiaH you're right, I didn't think about ECU calibrating. It is given every software have some bugs, however with complex algorithms behind this technology, there is a lot of things going on, on purpose that only Toyo engineers know about, so I would give benefit of doubt first. To make things more complicated, I read somewhere few years back that Japanese car makers started using "fuzzy logic" in cars. Now I have no idea if this logic is used in TCH, but to simply explain to non computer person, normal logic has 2 states - something is either 1 or 0, true or false, in fuzzy logic things could be 40% true or 5% false for example, making software logic so much less predictable. I see my car running for no apparent reason often enough, but I think there is some logic in it's madness and it has patterns.

 

Try pressing the 'ECO button' located a few inches to the right of the fuel door button. ECO, (economy) helps with the heater and AC when turned on. I found it helps to turn the engine off when at red lights or at stop signs. The ECO indicator in the AC/Heater window will say if you don't move the Temp to Hi or Low.

Last winter, Tom in Denver mentioned how the ECO button helps. I tried with and without it, and the ECO helps keep the engine off when stopped at red lights.