Feel a "clunk" when letting off accelerator then pressing it again

Have you watched the HSI display to see if it is when the ice kicks in?

I found on our 2010 Prius II when we were around 120 k miles that there was a slight rough transition between the engine and motors. I investigated the egr system and cleaned up the intake manifold and this went away.

It could be an engine mount, but the engine should be loose all the time if that were the issue. If only under throttle, I would suspect egr and intake clogging.

Hope that helps.

 

How long ago did you clean out the system (excluding the egr system)?
Have any oil consumption issues? What gas do you use (top tier, whatever is available)? Ever try fuel injection cleaners?

 

No dash codes I assume?

One thing you could try is to remove the black cap off of the egr valve and move the plunger of the valve back and forth. As the miles pile up, the deposits may begin to prevent good travel of the plunger, causing lower flow.

I have an impact screwdriver to remove the screws off of the egr valve. If you try to use a regular Phillips screwdriver, the screws are in there good and you may round out the head.

 

I don't have one of those and researched reviews for a potential buy.

I saw this review: Impact Screwdriver Set with Case

"Hammerhead
Submitted 1 month ago
By Dan the toolman
From New Hampshire
Verified Buyer
I was drunk when I tried to use the tool. I smashed my thumb with the hammer and a piece of the bit chipped and hit me in the face. I have a huge scar from the bit and now I walk with a limp. I have developed a severe case of hammaphobia and I am afraid to leave the house except to buy beer. My medical bills are piling up and that's adding to my depression. I would recommend this tool to anyone who does not drink."

Since I don't drink much, should I purchase that one?

 

Interesting review and story.

I bought mine at Harbor Freight and it serves the purpose well:

Impact Screwdriver Set with Case

With a 20% odd coupon you'll probably get it for less than the song and less dance above .

 

My 2015 with 30k on the clock also has a slight clunk, both when I let off the gas or accelerate from a roll/ coasting. Wondering if it's normal? It's ever so slight, could just be my OCD kicking in

 

At your age and mileage it is most likely just the ICE kicking in or shutting off. Nothing to worry about.