intermittent, but frequent, loss of ICE power at wheels (2007)

Hi all. Long time no PriusChat. For the last couple of months, we've had a significant, but intermittent loss of power at the wheels, combined with really poor gas mileage (best has been around 35mpg, right before this started, we had actually managed a tank >50mpg). I hadn't come here yet to post about it, because I didn't feel like I had quite enough data to work with to explain. Now, after having put several hundred miles on it in the last few days, I'm pretty confident.

Symptom 1: Acceleration (particularly above 20mph or so) frequently sucks, especially when the pedal is down farther.
Symptom 2: Gas mileage sucks.
Symptom 3: When battery level of charge is extremely low, car refuses to accelerate. (this, I just experienced for the first time today, it hardly ever gets to a very low charge)

*editing in two other details here, that I forgot to post originally*

Symptom 4: Pushing the gas to the floor causes the engine to rev up as normal, but the car doesn't go forward (much, if any) faster than if I push it a quarter or so down.
Symptom 5: Putting the car in Engine Braking mode, then releasing the gas, causes the engine to rev way up, but the car doesn't slow down much if any faster than it would if it were in Neutral.

Codes: DTC P0A93, Inverter Cooling. This code has been present since we bought the car in 2012. It has not apparently caused any obvious points of failure, although my regular mechanic insists that we should have had it fixed by now, the costs they were quoting on it have been prohibitive, considering we've noticed no obvious driving issues.

HV battery was replaced (by GreenTec, using their 3k battery option, mostly for the warranty) in mid-June, problem started cropping up in mid-October. Only other non-oil/tire maintenance that has been done on it in memorable history was new brakes in early Spring.

Have taken car to two different regular mechanics -- my regular mechanic says "Not sure, but we think it's a problem in the hybrid system somewhere" (they don't do hybrid work). Then I took it to a dealer (our dealers here are total jerks, so I didn't want to do that), dealer tells me "Internal Engine Damage" and refers me to a car salesman. Then I took it to a shop that advertises being hybrid specialists here in the Detroit area. They said "Well, it doesn't act quite right, but everything is testing within normal parameters. And the dealer is full of shit, your engine is fine, although the spark plugs could stand to be replaced." ... so, i'm getting nowhere slowly here.

I don't know a whole hell of a lot about how all of this works, but it feels to me, relating my reasonable experience with non-hybrid mechanics, like there's some sort of transmission failure. What I don't know, is how to pinpoint it, or how to tell a mechanic what to check. We're at a point where we basically don't know what to do. But we need this fixed.

I'm in the metro Detroit area, and would greatly appreciate any advice that people can give as far as mechanics that might actually be able to diagnose/repair, or advice for doing it ourselves (or finding competent hobbyist mechanics that could help...)

 

Just Inverter Pump. Which has been present since a few miles after we drove the car off the lot of the dealership we purchased it at, 6 years ago. When I inquired with that dealership about the code, the dealership told me in no uncertain terms, literally, to go f- myself. A second dealer told me that it was an erroneous code, and that the part was operating normally, and that it's replacement under warranty on the recall had been performed before I purchased it. Toyota's query website confirms that the original dealership I bought it at *claimed* to have replaced it under recall (considering their attitude, i don't believe it) . . but another 3rd party mechanic also said that it appeared that the pump had been working correctly, and suggested that the car would halt if the pump were failed.

238k. Problem started around 232k.

I'm failing to understand how this would cause an intermittent problem, appearing ot be ICE related? starting in about October of this year, after that code has been set for the last 6 years. (see above for story of my troubles related to this code, but I've never had any noticeable mechanical issues with the car until now) I would appreciate an explanation of how this could be related, in which case I would consider approaching someone about fixing it.

 

... not that i don't want to get the water pump thing fixed and clear the code, but it's not particularly important to me if it's not the cause of a driveability failure -- and this is the first time anyone has suggested that it might be. Just right now, I'm unemployed, and my other car is down, so I absolutely need to make sure that if I'm spending money on something, it's something that is going to have a good chance of fixing the driveability problem.

 

Seems unlikely. I'm not sure how to determine that on my own. It's not exactly limping -- the engine is running at full bore, but the harder the engine runs, the less the power goes to the wheels. I think I may have forgotten to list that in my OP. I should probably go back and edit that in.

Symptom 4: Pushing the gas to the floor causes the engine to rev up as normal, but the car doesn't go forward (much, if any) faster than if I push it a quarter or so down.
Symptom 5: Putting the car in Engine Braking mode, then releasing the gas, causes the engine to rev way up, but the car doesn't slow down much if any faster than it would if it were in Neutral.

 

It's been years now, but I think it was around $600, and we didn't have the money at the time, as we had just put our everything into buying the car. Now we don't have the money, but we'll have to, if that is the source of the problem.

I check and load the oil regularly, the car is consuming about a quart every 5k. It always has. I'm not familiar with the inverter pump or how to check it's fluid level? I'll google that, but details here may be helpful too. Mechanic checks all fluid levels when they do tire rotation/oil every 6k, and have never noted any problems. I also check the engine coolant when I'm checking the oil, as I've had coolant issues in other vehicles before, but have also never noticed any problems. Don't know how to check from the radiator, versus the overflow, though.

Mechanic code check. I also have a cheap-junk-grade scan tool, which I can use when I have access to the car again (right now, it's in use elsewhere.. we unfortunately have 4 adults and 1 car right now). If it shows anything else, I'll return and post that.

The other half says that it seems that the problem happens less after the engine has got up to a running temp. I disagree, and think it's pretty much happening at any point. She didn't even notice there was a problem, though, until I had her floor it one day at 20mph, and we didn't accelerate any faster.

I don't even know where the inverter pump is, what it looks like, or what i'd be looking for when touching it or looking for surface movement in it's reservoir. I can probably also google those, but I'd also appreciate any further details.

It *was* my understanding that the original inverter pump had a recall out on it, and that a failure of said pump, would cause the vehicle to not drive. Apparently this understanding needs to be changed a lot. (and we've had the car since 125k I think, who knows when this part may have started to fail .. the CEL on it is intermittent, but the acceleration problem occurs regardless of the CEL)

 

Thanks for the vote of confidence, I'm sure that I can do this. I'm not mechanically stupid, but I'm also not particularly mechanically learned, either.

 

hey, fun follow up: i haven't touched anything under the hood at all, but it just spent the last 60 mile drive, with absolutely no problem whatsoever, driving as it did prior to this starting in October. I half want to attribute that to the fact that it's a surprise 45 degrees here right now, but we've had other 40-60 degree days since then also, that it has not acted right at all during. I've got a 62 mile 46mpg going right now, after months of doing 28-34-ish, and every time i put the gas down, it accelerated mostly correctly.

This may also mean that whatever the source of the problem is may be very difficult to detect. :-S

 

I didn't mention it earlier, but the 12V battery was replaced in November, for being suspected of a problem (100s of codes were set, mechanic shop told me, when we first brought it to them to see if they could diagnose this new problem), and then again last week, for it being an actual problem (there was no juice available at all, i have suspicion that a plate cracked from the insane potholes going around)

 

yeah, the second battery was covered under warranty.

Since I wasn't able to get home until after dark, and I'm not equipped to even kind of do night-time looking at things, I am holding until after I get home from my first errand of tomorrow, to take a look at the things I've been asked to look at . . . will need to get it home, while it's light, and let it sit for an hour or so to make sure it's cold enough to go poking around in hopefully not-pressurized coolant systems.

 

Chap,

Thanks for the detailed reply. Clearly, you're far more experienced than I am on how these work I'm not challenging what you're saying, but I do want to make sure that all of what I *do* know makes sense with what you've said, and that we are both fully understanding each other . . . so I have a question or two

Does that make sense, then, that the engine would rev up as normal, seemingly not providing any power to the wheels, while still charging the battery? ie, if I floor the accelerator, I only accelerate about as fast as I can on battery power alone (and it drains my battery fiercely). Going at decent inclines at highway speeds, I feel like it's very difficult for the car to make it up, and the engine revs significantly higher, with little to no additional power output at the wheels.

I'm asking this, because that's the part that isn't fully making sense to me -- but I'm also approaching the problem with far more experience in software, since i have a background as a software engineer, rather than in hardware as a mechanical engineer. I would think that if the car was going to refuse to accept the engines input, then it would theoretically also refuse to let the engine wind out like that. But I don't know the mechanisms involved, if that's even possible. And that's why I'm asking those who know a ton more about it

And the other question that isn't at all making sense to me -- if this code has been intermittently set, for as long as we've owned it (and I'm going to guess quite a while longer -- the dealer very likely ensured that it was reset before we tested the car each time, and it wouldn't surprise me if the original owner of the car may have traded it in because of a CEL that they couldn't get rid of) -- why is it only *now* manifesting itself? After well over 100K miles put on it since then? Is it a situation, where it checks a sensor or something, for example, 5 times, if it fails 5 times, it sets the code, but then it has to pass hundreds of times to un-set the code? In which case, it could've been slowly failing more and more over time, and we've only just now noticed because it's failing more often than not?

...So, over in the "common problems" thread on this very forum, it actually says this code relates to "power loss". That could probably use a much more thorough explanation of exactly what it means by "power loss". To me, reading that, I assume either "electrical failure" or "car doesn't go". This problem where it *feels* like mechanically everything is working as it should (ie, the engine revs like it should), *and* according to mechanics, everything is testing within spec, but it's just not being transferred to the actual drivetrain .. sounds like that could use more explanation in that thread.

.... and, lastly, I'll be talking with someone at Toyota HQ tomorrow about how crappy the two dealers that I've dealt with over the years are. I'm sure very little will happen as a result, though. I'll be doing that *after* I pull the codes using my junk-grade Bluetooth code reader, and try to perform the tests and inspections that were outlined above.

Again, thanks for your input!! Very much appreciated, everyone.

 

Right, I think I didn't explain t hat too well on "what i think when i read that a little bit ago" .. i was thinking, when i read that initially, just describing "power loss" i wouldn't expect to have the engine firing at full capacity, and the drivetrain not following through. I've had plenty of vehicles where i'd describe a "power loss" as "the engine doesn't go like it should" . . .the only time I've ever had the engine go freely on it's own, when it should be moving the vehicle, is when the clutch in my '85 S-10 exploded in a partially engaged state, allowing me to maintain a speed, but i couldn't get it moving on it's own. Which was absolutely hilarious when my buddy hooked up a tow-rope with a disconnect mechanism to his pickup, dragged my truck out onto the highway, and hit the disconnect, allowing me to maintain a nice 55-mph until we had to exit the highway, then we stopped at the exit, hooked the vehicles back together, and towed the rest of the way home. Strangest thing I've seen/done in 24 years of driving. In hindsight, it was probably as dangerous as it was hilarious. :-S

ANYWAY . . . if this does turn out to be a problem with this pump (and why is it suddenly apparently working, coincidentally while it's warm out?) or something related, maybe that will turn out to be far cheaper than the hybrid transmission system.