Vehicle Drives Slow, No Dashboard Warnings

Hello.

Trying to get some help in understanding what the problem might be before I go in for maintenance. Concern is the problem is intermittent, so it makes it hard to just drive in and get a fix.

This is a Toyota Prius 2013 that I've purchased new, with 31k miles on it. No accidents or major repairs, I've been changing the oil and had tires replaced/aligned after the first appearance of this problem (not sure if relevant but these are the only maintenance I've done thus far).

The Problem:
Perhaps since 2016 I've had a problem where I turn the car on, and when accelerating the engine will sound like its working *extremely* hard, but not give a comparable amount of acceleration to the vehicle. This becomes particularly noticeable driving on a heavy incline.

That said - I can still drive the car, get on the freeway and drive around fine - I just need to give it more acceleration to compensate, and the engine makes much more nose (nothing abnormal - just that its working really hard and not getting sufficient "umph" for the work)

Sometimes if I turn the car off, and quickly turn it back on again it will start driving normally like nothing was wrong. Seems to indicate its some kind of programmatic or electronic issue.

This problem only on average once every 2 months and if turning the car on and off won't address it, leaving it off overnight will. Doesn't particularly inconvenience me, and at first I just figured it was a fluke, then hoped it would get worse to the point that I could consistently reproduce it. No dashboard warnings light up while in this "slower than normal" state.

Any thoughts on what it could be?

 

Mileage: 31,000
Location: California, Burbank

When does it happen: Definitely no association to rain. Generally, I want to say it happens more often in the middle of the day rather than when I first start my vehicle up, but it is so infrequent its hard to say I am confident. Here is the most common situation that it occurs under, but by no means is the only time it occurs:

1. Car in parked state under shade.
2. Start car @6:30AM, drive to work (no issue)
3. Arrive @7AM, park with no shade outside.
4. Start car @4PM, drive to parents home (no issue, but there is a 10~ minute strip of going uphill),
5. Arrive @4:30PM, park in no shade outside
6. Start car @5:30PM, drive to friends home (issue occurs here, lot of downhill but slight initial uphill so easy to notice issue as car will lose ground if I don't press accelerator harder than normal [I've gone "backwards" before a foot or two before realizing])
7. Arrive @6PM, park with no shade outside.
8. Start car @8PM, problem may or may not persist.

That scenario plays out every Tuesday and I feel its happened during both winter and summer. My suspicion goes to the uphill climb, but it just doesn't happen often or consistently enough unfortunately.

I also vaguely recall the back-seat vent going somewhat louder than normal, but it may have just been a coincidence as its done that before as well. This may be extraneous information.

I may have to keep a log of what happens to get some better information. The infrequency is what makes this difficult.

Thank you for the welcome and the reply!

 

Total Trip from my home + each destination until the last is 26 miles.
The return trip back home which is not included above (without all the stops) is a total 18.5 miles.

Regarding engine - I don't know how to tell. If I assume this means, "after turning on, wait parked until the engine stops on its own then start driving" then generally no, only in the morning. I let it complete that cycle in the morning but not at any other stops during the day. Is this the information you're looking for?

Tire pressures - generally when I fill them I take them to 37/35. I am not ritualistic about filling them, but they drop around 34/32 when I realize "its time to fill up" again. Its probably about time to refill now so if there is a better value I am willing to try - but figure you just want to make sure the tire pressure isn't dropping really low + cold weather.

 

Erik - What would I ask for specifically? If I go to the dealer I'd probably have to explicitly ask to get anything beyond the usual tasking, so it would help to know what to ask for otherwise they'll just assume I want "the usual tasking report".

Bisco -

1. No, I know for sure because I've tried toggling the various modes to see if it would "shake out" of whatever state its in. I operate in "Eco Mode" 95% of the time. I want to say the problem persisted even if I ran in power mode, because that would have been a big clue if it had fixed the issue. I recall trying, and then inevitably going back to eco mode.
2. Average MPG for a trip I had going over 7621 miles was CONS = 43.7MPG and AVG = 26MPH
3. Wheel heat - Not sure. If I were to check, would touching with my hand be appropriate and should I be looking to see if some wheels are hotter than others? At the very least, never noticed abnormal heat but I don't check often enough to have a baseline for normal.

TMR-JWAP - OK, I was on the fence about buying an OBDII reader, perhaps I'll grab it and see if anything obvious stands out. Though it will be some time before I can observe this problem first hand.

Thank you for all the questions & appreciate any insight.