2007 with reduced engine response on cold start after sitting for 2 days

Someone I know has an 07 Prius with 191,000 miles on it. Whenever it's sat for more than a day, you can start it with no issue on a dead-cold start and back out of the driveway, but when you try to drive it up the hill she lives on, the engine has significantly reduced power up the hill. About 15 seconds into the climb, it finally responds, revs the engine high, and suddenly kicks in with power surging faster up the hill. There are no codes. This new happens when the vehicle has been driven within the last few hours and is only when it's very first started completely cold.

Lately, she's only been driving it about .5 to one mile a day twice a day, so fuel economy over time is difficult to judge. The vehicle is only running long enough to get the catalytic converter hot (so the engine is on and not in EV mode at all) the whole time it has been running.

 

Thank you, everyone. Although the readings on the hybrid battery seemed to always be good upon start-up, I suppose that could have been part of the issue. The engine seems to have developed a serious stumble since I posted but still no code. She took it as a sign and decided to trade it in for a different vehicle. Thank you all again. Take care.

 

For the trade-in? She got $2000.00 for it.