2008 Prius Loss of Power at freeway speeds

Thanks, I'll gently nudge him again.

 

Even in the absence of a total smoking gun, thank you so much for talking to him. Getting the second opinion helps me tremendously in terms of peace of mind.
I'll keep y'alls posted with what happens!
Ron

 

Absolutely possible in this Prius. It's done a lot of long distance trips between CA, AZ, UT, ID, and TX, you know, the cold states, and the drivers involved are the kind that'll do a 12-16 hour road trip in a single shot.

This almost certainly has the original fluid. The mechanic who has it now checked the fluid both as a matter of course, and because he feared someone at a Drive-Thru oil changers may have accidentally drained some by mistake. Confirmed the level was OK, but also said, "that drain plug has never even had a wrench on it".

 

Definitely an oddball issue, the deeper things get investigated, innit?

I harbor a little fear that this is going to be something silly like a bad crimp or a relay that's firing, but has gone internally resistive.

 

I resemble that comment.

 

That was actually my first thought, but the mechanic was able to reproduce it on a flat surface at freeway speeds. Also, she drove the car from CA to UT over I-80 / Donner Pass and didn't freak out (it's about 7000' of climb with a lot of up and down leading to the summit). Still possible that's the cause, but I doubt it at this point.

 

Hmmm. Good to know. I'll definitely keep this in mind. It was a little low on oil when she got to UT. I don't know how low though. Again, not there to be an eye witness, so it's hard to say. In my driving, I haven't noticed the battery being low, but it's definitely original, and I'm still new to the Prius myself.

 

So far that's been the only time it's been noted.

 

shtuff happens indeed!

 

Just wanted to updated where we are on this.

The Prius is still in UT. Wife borrowed my mother in law's car to get home, MIL is keeping the Prius for a couple weeks to make sure it's OK before we get out of range of the garage that's been working on it.

We did end up replacing the transaxle with a used unit from a car with around 65k on the clock. This seems to have fixed the loss of power issue. It's been driven for about 200 miles over the past week or so, both in-town and freeway driving, and behaved as expected.
FWIW, the mechanic reported the fluid in the original unit looked, and I quote, "weird". Like maybe it'd been contaminated, or was overused.

-fast forward to now-

A nephew was driving it last night and got red triangled as he was getting near the house. He took the below pic of the MFD when this happened, and it's since been back to the garage. Mechanic said that the only thing he saw out of the ordinary was a loose negative clamp on the 12v battery. He reseated that and the car appears to be behaving itself so far. Mother in law (first owner of the car) is driving it now and reports the battery SOC is where she would expect it to be for the conditions in which she's driving (she admits to being a gauge watcher; I actually trust her on this). Park is entered and exited as expected.

Comments welcome, and thanks again for all the help!

Ron