Power Loss- Suggestions

It sounds like when they drove it around the lot and it dropped fast, you parked it, they came out and started it, then drove around. If so, then they were in the warmup stage it is supposed to use the battery more and keep the engine running but minimal to no power to the wheels until it warms up. So I wouldn't worry about that.

Have you replaced the transmission fluid yet? And what oil did they put in, and who is they?

 

Mass flow sensor? Perhaps it needs to have the throttle body cleaned.

Tom

 

Is the original 12v battery in the car?
A misfiring spark plug should set off a code but might not???

 

I would go to an auto store and buy 4 quarts of Mobile 1 0w20 oil. Tell them to refill using this, and that there should be somewhere between a half bottle to a quarter bottle left over when they are done. Get the bottles back before you leave, and if you don't know how to check your oil level have one of them show you that the oil is between the 2 bumps and not higher or lower than either. There is no Lexus model that takes 0w20, so it is doubtful that's what you got. Our Lexus dealership while offering nice free muffins, has little that will service the Prius.

If the ATF change hasn't been done, then I would do that. You NEED Toyota brand Toyota WS ATF. It will cost about $40 for 4 quarts. You do not want to "flush" the system, as there is no torque converter or squirrly bends to hide fluid. Really all you do is open the drain plug (10mm hex) and watch it pour out. Then close it back up, open the fill port above with a 24mm socket and pump new stuff in. Presto chango. Toyota says it is "lifetime" fluid and doesn't need to be changed. However the consensus is that it should be changed initially at 30K and then every 60K after that at a minimum. So with the mileage on your car, I would just do it. For $40 and an hour of your time, it is pretty good insurance.

Good question on the 12v. I don't think this would cause the power loss unless the SOC was already at 1-2 bars because of the 12v. But it is a good preventative maintenance item as well.

A single bad spark plug makes no code. But 2 bad spark plugs do.

 

You put alot of miles on that car. Averaging 31,000 a year. I hope your doubling up on the maintenance.

Trans fluid should be changed every 30K miles.
If it was me I would change the Inverter coolant every 30K also. Its very easy.
Oil change every 7000 miles.
Way overdue for new plugs with special attention paid to the Ignitor connectors and check for any signs of water damage from the windshield water dam seal possible leak.
Periodic cleaning the the throttle body and MAF sensor.
And a new 12 volt battery if you still have the
original battery.

And lastly to address your current problem did you check your VIn to see if you are on the Inverter Coolant pump replacement
campaign? Sounds to me you lost your coolant pump.
Check for turbulanece in the Coolant reservoir while the car is in READY.

 

I just changed my 12v battery in my 06 with the new Optima battery. The gas engine fells smoother and less fluctuation during the idling part (before reaching Stage4). I have 151k miles and it reminds me of the feel when I got the car.

 

Mountain driving can be hard on the HV battery. The big question, can you hear the HV battery fan running? Have you ever cleaned the duct for the HV battery fan? It is probably clogged with lint if you have a carload of dirty teenagers all the time. Do you ever park and shut off the car at the bottom of the grade with 8 green bars? That's also really hard on the battery, and you may be due for a replacement. Problems there can be a source of hesitation and fits the huge state of charge swings that you and the Lexus tech observed. You can get a reasonably priced refurb'd battery from Adopt-A-Part in Boulder. For now, drive it until it gives you the red triangle.

 

Are you sure that you're not just feeling the warmup algorithm? The car tries to NOT use the engine in warmup (first few minutes of driving) and relies mostly on the battery. If you give it enough go-pedal pressure to where it thinks you need power now and lots of it, it will engage the engine and use it. So you will get an extra umph of power when that happens but as soon as you say a little less power, it will free spin the engine again until it's warm.

 

Declining MPG is another indication of impending HV battery problems. 157K miles, Rocky Mountain driving, 2005, lower MPG -- I think you need to prepare yourself for a replacement in the coming months. It is possible that it will limp along for a while, especially if you drive it daily -- less likely to see problems due high self discharge in a weak module. I don't know where you are in CO, but do not go to Toyota in Grand Junction.

 

1.5hours away from a dealership in Colorado means you are either out in the east-boonies where's the cows and corn roam or you are in the west-boonies living on a giant rock. Guessing the 1.5hrs is to Denver?

If you are in the west and it lived most of its life going up passes for 150k+ miles, I think seilerts is correct.

Now the good (depending on how you think about it) news is that you can get a Hymotion plugin with rebates from the state of CO installed (in Boulder I believe) that 100% replaces your original pack. So get the upgrade and a new battery pack. I am essentially waiting for my pack to kick the bucket or pass 100K, then I am starting my personal PHEV conversion.

 

Glad to hear that Eric helped you out. Anybody with a Prius problem in Colorado should start at Adopt a Part.