2008 Prius losing power - Need troubleshooting help.

Is there a way to check the health of the HV battery?

 

I checked it on Friday and found no difference in the 2 acc pedal positions at all, not even a decimal change. I found this interesting article where the writer is claiming that he was able to adjust the throttle position sensor using techstream. Wondering how can one do this? What V9.30.002 MINI VCI for Toyota TIS Techstream can do? | OBD365.com Official Blog

 

So since the problem was not completely gone, I went ahead and changed the 4 injectors yesterday and the results are encouraging. The ride is more smooth, less vibrations, better power, lower engine sound. The misfire during cold start up still there. I did find one of the injectors with gunk in it, most likely was the problem and which would get temporarily fixed with injector cleaner in the tank, still have some so will find out when I have the next tank of Chevron with no cleaner. I always used Arco, not sure if Arco did this, but have decided to use Chevron only.

One unusual thing has started happening, the first time when I replaced the throttle body, this happened a couple of times, upon stopping the car on a light or stop the engine would suddenly rev up high as if the gas pedal got depressed, my foot would be on brakes, I got surprised, since yesterday this is happening almost every time when I slow down to stop. Is the car relearning the pedal movement?

Here are the pictures of the interior of the injectors.

Here are some more images of the bad one only.

 

Yup no DTC's are being logged. Just because it is known that the coils go bad in prius I will change all 4 next week to see if that goes away, if not I will leave it at that. Until now I am satitsfied to an extent as I was able to catch 2 problems and resolved those. One being sticking throttle body and another being one clogged injector.

 

Maybe about 25% still remains, I would dedicate a portion of it to the heavier softer tires that I have (Michelin Defender 205/60/15, already broken in at 5K miles now). I feel like blaming the misfires to the remaining portion, some times I have also noticed the misfires when the car is driven although less compared to when it is cold.

 

That is exactly what Avi said, btw I met him last weekend and he was speaking highly about you. I will still go ahead and try doing that especially knowing it wont hurt. I got a set of 4 oem, new bulk packaged coils for $140.

 

OK so you were right. Replacing the coils did not stop the misfires however the drive got a little better, just a tiny bit. I have always used regular oil for oil changes should I change it to synthetic at this age (92K), once I had asked a Toyota advisor and he strongly advised against, stating that at this age the engine is already broken in with the regular oil, changing to synthetic might cause harm to the engine, is there any truth in this?

 

OK so finally the root issue was found and fixed .. Thank God!. Tell you what, these new cars are reducing the smartness of humans as most of the mechanics I showed my car to said there was no issue as no code is coming up, now finally about 3 months (in July 2017) ago that code came it and it was "P0420 - Powertrain Catalyst System Efficiency Below Threshold (Bank 1)", also thank God I am California, the catalytic converter was under warranty until 150 K miles, I had 120 K. Once they replaced it and after running couple tanks my car is very close to normal. The first time I noticed the issue was around 75 K miles, so it ran under this condition for around 45K miles and I believe it has caused a permanent damage of approx. 5% to the engine etc. I have the power back, gas mileage is right there. Thank you all for your inputs.