Discussion in 'Gen II Prius Fuel Economy' started by scramjett, Jan 23, 2012.
I figured as much. My mileage has dropped to high 30s/low 40s.
Ok, so, I'm assuming the inverter coolant reservoir is that reservoir with pink coolant next to the inverter? If so, I pulled the cap off and the bottom had liquid pink coolant on it (no powder). The threads of the cap had a white powdery substance on it, but I suspect that is not a concern no? So, if I'm right, that's not it either. This still leaves checking the fuel injectors and if something is dragging on the wheels/tires (ie see if they spin freely when on blocks).
A side question: where the heck is the engine coolant reservoir? I saw what appeared to be another reservoir sitting atop the radiator, is that it? Does it take the standard (green) engine coolant? I couldn't tell because it was very hard to see what was in the reservoir since it was covered.
As for the throttle body, given the number of people who do not clean it on a regular basis, I'm going to consider this as a maintenance item to work on at a later date and not related to my problem.
Yes the white powder. Time to replace that Inverter coolant imho.
Buy a gallon of SLLC at Toyota dealership. Pour a little of that SLLC in a glass and then take a sample out of that reservoir and compare.
You'll see what I mean. SLLC is super long life coolant.
Its really easy to change that Inverter fluid. Only hard part is opening the transmission coolant drain plug underneath.
Have to raise the car a littl to get under there.
Let it drain. Fill it up with the SLLC and then with car in Ready
open the bleed petcock in front of the Inverter. You have to take off the black plastic valance cover that covers the top front of the engine compartment to see that petcock.
Thats easy. With a phillips turn the screw out while you push the screw from undeneath and it pops right off.
btw, the bleed petcock up top is on really really tight so you have to hold it with a wrench while you un-wrench it
so you don't snap it off. Open the beeder till fluid comes out. DRive a little and do it again basicly.
There's a few You Tubes on it too. Its easy.
Yeah, I'm probably going to need to watch some of those YouTube vids. I'm a visual person and I don't know the names of half of the items you just rattled off above.
Maybe I can just wait until the 60k mile service. The maintenance schedule shows a radiator flush at that interval. Additionally, since I'm not quite at the end of my 7 year extended warranty yet, I don't want to start screwing around in the car and give them an excuse to void the warranty.
I have been delinquent in replying to some questions earlier. I have been traveling for work a lot lately.
As for servicing my vehicle recently - it was taken to a dealership by my wife while I was out of town. I didn't get to look at the injector, shop said it needed replaced and would be covered under the warranty. Oddly, the engine still start/stops a bit rough.
Just filled up my second tank since the work and I have seen a bump of 5 mpg. Battery behavior is still a bit strange on the uphill in that it doesn't go into full battery assist but shows assist and simultaneous charging while at 6 bars (used to do the same when in green zone but it doesn't hang out in the green zone anymore). Oddly, now the car now uses very little electric assist and charges most of my 40 mile drive, then when it hits the first green bar it goes to full battery assist until it is down a bar again boosting my MPG from 42-45 to 65-70 - this is a change in behavior but my average MPG is back up to 48 to 50 mpg overall so it is tracking where I would expect.
There is something I have noted during all of this - the rear tires look like they need aligned since they look a few degrees off of vertical but I was told that they are not designed to be aligned. Seems odd since all my other cars required a 4 wheel alignment, my old Ford used shim kits for alignment. I know this could put a hit on fuel economy and the pocket book for tire wear so I plan to check into it further.
Good luck, I will post if I come across anything more.
That means that some of the power generated by MG1 is going off to MG2 to power the wheels and some is going to power the cars general electrical systems and/or charge the HV battery. Still sounds about normal to me.
The rear wheels are supposed be one to two degrees off vertical (-ive camber = tires slightly further apart at the road than at the top).
That is odd that the MG1 and MG2 Behavior sound normal - that means my car has never been normal as I commute the same hill 5 days a week and this is a change from the car's normal behavior. Not sure what to think about the implications that 50k miles of normal weren't really normal.
As for the camber, I realize that some cars will have a degree canting off vertical axis but currently it looks excessive on my car. Enough that I could use a plumb and protractor to measure it. Either way, I will have the alignment measured at a shop and compared to spec and I am more comfortable that corrections can be made after finding that a prius specific aftermarket shim kit is made for the rear wheels.
I mean that both of those behaviors are within the normal range of what you should expect. It's very common under the conditions you describe to have it flick between battery assist and none. If the prius "thinks" that the engine is providing enough power then there's really no point in providing battery assist. The temperature or the exact state of charge (6 bars is fairly broad band) may influence exactly how much of each (assist or none) that you see on any given day.
Is the camber such that the tires are slightly more widely separated at the base or at the top?
The alignment for the rear wheels is not adjustable (by Toyota). A prior Toyota tech and current forum member has put some shims in for some of us that had out-of-spec rear wheel alignment, but Toyota won't do it. If it's that far out I have to wonder if there's been some damage, maybe a curb hit hard by your wife that she forgot/neglected to tell you about?
I think the behavior snowhound2 and I are trying to describe is not that the car will flick between battery assist and engine only assist, its that the car will actually charge the battery AND power the wheels under heavy loads such as going up a steep grade. Up until recently, I've very rarely seen the car run the engine to both assist the wheels (using MG1) AND charge the battery (usually only happens when down to 2 bars of charge). Now it seems as if I'm seeing it rather frequently, starting at around 50,000 miles as in snowhound's case. In fact, I quite often see this behavior in the green zone at 7 bars of charge. As I've stated before, I always thought that 6 bars was the Prius "comfort zone" in that it always wants to be at that charge level. Because of that, I would think that the car would use battery assist until it gets back to that "comfort zone" and then it would do what I've always observed and what uart mentioned, flick between battery assist and engine only assist (MG1 only powering MG2, no charging). My car still does that, but at 7 bars and has been throwing in the "(MG1) power wheels (via MG2) while simultaneously charging battery" behavior for whatever reason.
Just to make it clear, we're talking about seeing an energy monitor screen like the one in the attachment right (except with more bars on the battery SOC).
Ok, the first thing to realize is that MG1 functions as (among other things) the equivalent of the alternator in a regular car. Thus it provides power for the ignition and other 12V accessories (via the HV system and the DC-DC converter). So technically, just because we see arrows going into the battery doesn't necessarily mean that there's any net charging occurring. If I hold just the right speed and RPM I can drive for hours at a time on flat roads and see almost always arrows into the battery, yet still never charge above 6 bars.
When the engine RPM is high, such as when climbing a hill, MG1 will almost always be turning in the same direction as the engine, with a reasonable speed and torque, and thus be generating a reasonable amount of power. If this power isn't desperately needed for the battery (eg SOC very low) then it will go to power MG2 and the wheels. This is where the bulk of MG1's power is going under these conditions when the SOC is good (eg 6 bars). Even if the SOC is good it may still take a small amount of power off to the battery, just to cover the losses due to the routine current demand of the other (non drive train) systems.
Yes. In the past, I had rarely seen this screen and its usually at the bar level indicated in your attachment. Ever since I started noticing the problem back in October/November, I've seen that screen more and it is quite often 6 bars or 7 bars when it does it.
Sorry for the late reply, its been a busy week.
Yes, frequently when driving on a level freeway at around 70 - 75 mph, I will see MG1 "charging" the battery which I had always figured was part powering the 12 volt bus and part "battery maintenance" (essentially switching between charging and discharging, kind of like what a cell phone does when its at full to prevent overcharging). In the past, "battery maintenance" occurred at 6 bars but since the problem started, it has been occurring at 7 bars in the green zone. This is counter to my understanding of how the HSD is supposed to work.
This is my understanding as well. When the engine RPM is high while climbing a hill, what I have observed is that MG1 is providing power to MG2 and the wheels and sometimes the battery assists MG1 in powering MG2. Some more shallow hills, the battery may not help. However, when the battery was at 7 bars or greater, the battery would always help until the charge dropped back down to 6 bars, regardless of how steep the hill (or how hard the acceleration) was. On steep hills where more power was necessary, (such as the Grapevine) the battery would need to help out more and it was not unusual to be down to 2 or 3 bars, sometimes even 1 bar. What I have been observing lately is that the car seems to be doing "battery maintenance" at 7 bars and will do at 7 bars what it used to do at 6 bars. Additionally, instead of the battery assisting on steep hills, it seems to continue to perform "battery maintenance" with the barest minimum amount of help possible. Since the problem started, I have been seeing the charge level at 5 or even 6 bars by the time I'm at the top of the grapevine.
Despite what Evan and several others have said about the car behaving normally, I'm confident that the car is not behaving properly. Or, to be fair to Evan and the others, it is mostly behaving as it should, just not at the right battery level.
I haven't been able to do much about the inverter coolant yet, as Ed(?) suggested (my 55k service is coming soon, maybe I can do something about it then) but the problem does seem to be related to something within the battery management system. Since resetting the computers didn't work, maybe it is something with the electrical and maybe replacing the inverter coolant might actually fix the problem. I'm at a point where I will give anything that sounds like it could fix the problem a shot.
I do think you have an issue.
But you need instrumentation to figure it out. There are numerous options: ScanGauge, PriiDash, Torque, AutoEnginuity, Techstream.
One thing I have wondered is what your battery itself looks like. Lint in the battery fan is one thing; the battery itself can get really dusty/dirty. That can insulate the cells, cause poor airflow, and create hot spots. The battery may scale back the amount of current that it will supply if it is too hot. So monitoring the battery temperature is definitely one thing to look at. If the temperature is high, you may have to take everything apart to clean it.
It is very unlikely that the dealership will acknowledge any sort of problem unless you get battery overtemp DTCs. So you may be on your own even after a diagnosis has been made.
Scramjett, did you ever figure out your low mileage problem?
I'd like to know as well.
My Prius dropped from 375 - 400+ a tank to 250-275 a tank and almost always dies fast to red bars and the engine now always seems to trying to be charging with little success.
I can barely get going most of the time. I used to get 46 -50 MPG all the time, now I am getting 34 - 38 MPG.
Hi goti. While still only a small minority, there does seem to be a number of owners reporting similar problems. There's always the obvious things to check, like brakes aren't dragging and the 12V battery is healthy and that the throttle body is clean etc. But many of the people reporting symptoms like yours never seem to get the issue resolved. I'm starting to suspect that the problems you (and others with similar issues) are experiencing are to a weakened traction battery. You'd hope that the Prius would detect this and throw a code (which would make it a warranty case) but in many instances of gradually weakening battery this doesn't seem to happen.
Can you give us any more details about how this issue started (when you first started noticing SOC anomalies) and how it has progressed. I also find my Prius performs pretty poorly when the SOC is down around 1 or two (red) bars and try as much as possible to avoid that situation. Surprisingly just allowing the car to warm up for about 45 seconds in park (with engine idling) before driving can help this (for me it happens more when the engine is cold because it uses the traction battery more heavily during this time). But if you're getting low SOC more often during regular driving this might not be of much help to you.
Have the people at Mellors Auto in north Florida (West Melbourne) take a look at your Prius.
Good people and they know hybrids.
You're not too far from two great independent Hybrid repair shops in the SF area. Get to one of them.
Luscious Garage | Hybrid Specialists
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