2015 Prius Misfire (Egr, manifold, engine replaced)

Hello,

My story starts with a mistake I made that lead me to this situation.

I had recently went to the dealership for an oil change (145,000 miles) and was recommended to have the PCV done as well as a coolant flush and top off. Coolant level was slightly low for the engines and hybrid not below min but slightly above.

I was heading out on a trip so decided I’ll buy the coolant and top it off myself did the engine reservoir first and did the hybrid second. Missed putting the cap back on the engine reservoir and drove over 400 miles. Second mistake was installing a phone mount right in the line of sight of the check engine. When I was almost home car started to lose power and that when I realized the check engine light was on.

Car over heated had it towed to a shop (not a dealership) decided let’s just put an engine in it. Mechanic let me know that he found coolant in the exhaust and intake. So other things might have gone bad but we will start with the engine first.

Used engine installed started to over heat turns out had a bad water pump. Luckily the original water pump was still good so he put it in and off I went. Drive good roughly one week. The started the weird misfire in the way home from the store got home let him know following day drive it 200 miles no problem. Went two more days no problem then when I was getting to work, almost about to park it happened again. Happed a few more times and took it back to him.

He cleaned the EGR, then we replaced the EGR, he let me know that it needed a reflash and I needed to take it to the dealership (mechanic was a former Toyota hybrid tech). He also tested engine for compression issues and came back fine.

Dealership recommended I replace the manifold and they started trying to diagnose the problem throwing parts at it replaced the plugs even though they were new wanted to replace the coils but after asking them to test by swapping coils around the ruler that out. This took about three weeks to get to this point and they finally said the boriscoped the cylinders and noticed coolant in cylinder one. Also said I could have a bad transaxle due to noise no codes.

My mechanic already had an engine waiting did a warranty claim so took it back the engine he got was clean and came with an engine egr and cooler. (Cooler was not replaced but he did try to clean it)

Still misfires!

He ran through a few sensors and found an O2 sensor wasn’t getting a reading.
open the exhaust to check the catalytic converter ( was not clogged)

what I know is the original egr was stuck and needed to be replaced, replaced the egr, intake manifold, has new plugs, good coils.

The engine runs once it’s given gas the misfire will stop as soon as you let off misfire is there. Speeds above 50 mph it drive good below 50 misfire is present.

Neither of us now what else it could be he believes it could be a control issue.