Car is a 2016 Prius Three. 206,000 miles. So I started having really rough idle when car shifted from battery to engine start or when I would begin to press accelerator. I initially got a CEL then two days later the car would start off with a rough engine start. Finally I got the warning "Check Hybrid System. Find safe place to park". Had the codes pulled and got P0300, P0301 and P0303. I ended up purchasing and installing Denso iridium OEM plugs. After about 20 minutes of the test drive started doing the same thing only this time I got a CEL but not Hybrid alert. Ordered new Toyota spark plug paks. Installed those today and I started having similar issues. CEL popped up so have the codes read again. This time only getting the P0303 codes and no secondary. Not sure what to check for now. Is it possible injectors causing an issue? Possible coolant related?
Is this the same car that you posted in another thread that's flashing the high temperature lamp???? You may have popped the head gasket by running the motor hot. FYI; the high temp lamp doesn't get saved in the error logs, so your engine water pump may be intermittent, cooling fans may not be running, stop leak in your cooling system (clogged), or popped head gasket. Possibly a combination of the above listed. Sorry
How long have you had it? EGR system ever been cleaned? Very common 3rd gen issue is head gasket failure, leaking coolant into combustion chambers, typically starting with cylinder one (left end of engine as you stand facing from front of car). Borescope inspection looking for evidence of coolant is usual first step to confirm.
