2007 Low MPG -- Can't figure out why

Re: 2007 Low MPG -- Can't figure our why -- Update III

He probably did. It was awhile ago though so I don't remember exactly how the conversation went. I was just more annoyed that he was focusing more on inconsequential stuff and not listening to me when I said the car was behaving abnormally.

Yes, that is still a nice feature of the K&N filters, however, as Evan pointed out and I discovered, the oil from the filter gunks up the MAF sensor. Probably wouldn't be a bad idea to clean the MAF sensor every time you clean and re-oil the K&N.

 

Re: 2007 Low MPG -- Can't figure our why -- Update: NOT SOLVED!

Hi all,

I am now officially frustrated! After my trip to SoCal over the weekend, I must report that I am still having problems. At first, it seemed like replacing the 12 V battery fixed it, but those were all relatively short trips. On the long trip, the car slipped back into its "old habits" of maintaining the HV battery at 7 bars of charge (green zone) at highway speed and very gently using the HV battery on hills and grades. Case in point, the attached picture was taken while I was half way up the south end of the grapevine (leaving the LA basin) which if I remember correctly is a 6% grade. In the past, the electric motor would pull power from the HV battery almost immediately and wouldn't stop until I got to the top, depleting it down to two or three bars. As you can see from the pic, not only is the battery NOT providing power to the motor to help with hill climb, it is in fact CHARGING itself while the engine is providing ALL of the power to go up the hill. This is at 6 bars of charge! I've only seen this behavior when the charge level is at 1 bar! I've also seen it do this on hills with the charge level at 7 bars!!

I have no idea what is going on anymore or what the problem could be. Maybe the HV battery does have bad cells? My averages for this trip were 36 MPG and 39 MPG. This was while running at 40 psi on my tires (which I had just filled up last weekend).

Does anyone have any possible idea what the hell is going on?!

PS - I apologize for the blurry picture. My wife was trying to take it from the back seat while I was driving up the grapevine and trying to dodge all of the people going 45 (not truckers!).

 

Yes, I was going about 70ish MPH up the GV at that time.

I usually go between 75-80 mph on the SoCal trips depending on traffic. 42 MPG is about what I normally get on a SoCal trip.

Interesting. I wonder if most Prius' experience this and "self correct" or something. It would seem as if mine has chosen not to "self correct." The screen did fluctuate between that and powering the motor but the powering the motor instances were brief and I saw the power flow pictured the most (the second most common would be nothing going to or from the battery).

Thanks for the offer F8L, I'd greatly appreciate that if someone has any ideas!

 

That hasn't been my experience. My experience has been that when I climb the grapevine (6% grade) that the HV battery is mostly powering the electric motor with help from the engine. It does fluctuate between powering the motor and doing nothing (no powering or charging) but it is mostly powering the motor. It only switches back to the more conventional "engine driving wheels charging battery" once the climb starts leveling out. I monitor the energy screen every time I go up the grapevine (usually for fun) and I have never seen it do that before November.

Yes, this is where I am at with Elk Grove Toyota now. All I have is my instincts and my visual observations of the energy flow screen and the crappy gas mileage telling me something is wrong. It's all circumstantial and while it leads to one inescapable conclusion with me based on my experience, I can see how with others, there might be other simpler causes (especially if you're a service tech dealing with people who don't know anything most of the time).

Assuming your definition of "very cold" is below freezing, we don't really get that very often, at least not on the freeway that takes you from Sacramento to LA. Even in the dead of winter, the temp while driving to SoCal is rarely lower than the 40s F. As for loaded car and quartering headwinds, that is pretty common on I5 (freeway to LA) but we were running lighter than usual on this trip and the winds were not as strong as they normally are. I'd estimate that I should have gotten anywhere from 43-45 MPG instead. There are a number of us Prius drivers here in Cal that go 75-80 mph or more on I5 because it is a looooooong drive to LA. A 5 mph difference in speed could mean the difference between a half hour more or less on the road.

LOL, if I were any good at electronics, I would be more than happy to do that. I read through your posts and it does sound like a case of moisture causing a short somewhere. When I had my Saturn SL2, it had a receiver hitch with wiring harness that my dad had installed while it was still his car. After some damage to the left rear quarter panel caused a puddle of water in the trunk where the wiring harness happened to be, it would constantly blow the fuse for the cars running lights (all the other lights that are on when the headlights are on). I took it in to Uhaul (who did the original installation) and they found the problem was that an exposed wire was sitting in the puddle and caused a short. They basically said all they could do was pull the wiring harness to fix the problem. I told them to do that since I hated that I even had the stupid receiver hitch and had no intention of ever using it. You might try and find somewhere in the car that is pooling water and see if an exposed wire (or even just a wire) is causing a short. After the wiring harness was removed, I installed a new fuse and never had another problem. (I'll repost this in your thread as well).

 

Hi slohcinbocaj (can I just call you "slo?"),

Sorry to hear that! So far, I have not gotten the red exclamation mark and a couple trips to the dealership where they perform a "health check" (which is a fancy way of saying that they check the onboard computer for trouble codes) produced no error codes. They claim that the health of the HV battery is checked during a health check but I have no way to verify this (perhaps others can confirm if this is true?).

According to your profile, you are in Washington State correct? If so, you should know that Washington has adopted California's Low Emission Vehicle standards which include the 150k mile provision. I would check with the Washington State Department of Ecology to see if the same warranty requirements in California apply in Washington. Your dealership may be trying to gyp you (fun fact: it doesn't matter if you buy used, the warranty is transferrable).

 

As a matter of fact, this was the lightest load we've had in awhile. Under similar weather conditions and a heavy load, I've gotten around 42 MPG. As our son gets older, we find that the car gets lighter and lighter with each trip. Even when we loaded down the car and it was winter, I was always happy that we were consistently getting no less than 43 most of the time. I should also point out that this winter had been pretty mild compared to the last two for us.

 

Hmm, might be worth it just to see what the bars are showing vs the actual SOC and compare to your results. It may show something unusual. I'm not convinced that the HV battery is failing. It seems to me as if an electrical fault or computer glitch is causing the Prius to coddle the battery even more so than it normally does. It may not be a computer glitch though since the computers have been reset twice, once by Elk Grove Toyota and the other by me when I replaced the 12 V battery.