Gen 2 Prius vexing idle/missing problem

I have a gen 2 Prius with over 180k miles on it. Around 170k, the car started exhibiting a intermittent symptom where when coming to a stop, the ICE would not cleanly shutdown as expected. Instead, it would sputter and seem like it was misfiring for a few seconds prior to shutting down and sometimes shake the vehicle and dash pretty violently (this is not the typical "rough idle" that Prii exhibit sometimes, this sounds like the engine just threw a rod). When this condition was happening, it would also do the same thing as the ICE started back up when you taking off from being stopped, and as the ICE got fully started, the condition went away. No codes for missfire were or other symptoms were displayed after this condition.

At around 180k, the ICE was run out of oil. I had the entire ICE and trans swapped with one from a wrecked car with 75k miles. The swap went well but the intermittent problem detailed above remained with the new engine and trans. I took it back to the guy, he confirmed the issue and tried to resolve it. He has many wrecked Prii so he tried swapping the following to no avail: Another engine/trans, ECU, gas tank (with fuel pump), coil packs, and injectors. The problem remains and is still intermittent. It may happen right when I first start the vehicle or it may run perfectly on a 2 hour drive and then all of a sudden I come to a stop and it exhibits the behavior. I have a hacked techstream setup with an X-horse clone and there are no codes stored.

I have determined that when the behavior happens, if I turn the car off and start it again, it runs as expected but may start doing it again even on that same drive. Turning the car off and restarting right when I notice ithe problem does consistently resolve the problem in the immediate short term and that does not appear to be a random fluke. Another thing I've noticed is that when this behavior is going while I'm coming to a stop, SLAMMING (I mean violently locking up) the brakes stops the ICE cleanly. Also, when it has happened and I've come to a stop and the ICE finally shuts down after it's violent shaking/missing, when I let off the brake, the car kind of "lurches" forward in a continued pulse kind of way if that makes sense. Not sure if it is related.

I'm looking for ideas of where else to go with this. Anyone have any ideas to run down on this?

 

That's who changed the engine and trans and all the subsequent parts. He couldn't figure it out!

 

Hey guys, sorry I'm just now updating this post. I meant to come back with the solution but got distracted by life! Just in case someone reads this thread later and has the same problem, the issue here was the inverter unit! After this thread was posted, I started driving the car more for work and it started to throw a code DTC P0A63, but the car would still run the same even with that code thrown. This progressed to it later throwing that code, DTC P0A63, but not really wanting to move (just barely moving forward, luckily I was in a parking lot when this happened). Once that happened and I cleared the code, it ran fine and wasn't doing the weird idle thing at all. Took it back to Steve and he knew then that it was the inverter was bad. He swapped it out and it's been fine since. Still on the road today with 220k.