Hey all, I have a 2014 Prius four, that received a newer engine last Thanksgiving. One with about 40K in miles. My original engine had 131K and had to replace the head gasket, so I opted for a newer engine. At this same time last year my original engine had this same rattle at acceleration as the new one does now. my dad would say it’s cheap gas piston rattle. so it might be that, or possibly the piston hitting the lifter valves? tbh, I’m not really sure.
It only happens when I really jump on the accelerator (and not every time I do either) and it only rattles for a half second or a full second, then it stops. Never hear this rattle at idle or at low rpms
Pinging or preignition is different than a hg rattle. Pinging is a result of excessive carbon in the combustion chamber typically combined with a low hybrid battery at that point in time. So if it does not occur with the hv battery decently charged or it goes away with a full tank of premium then it’s pinging / preignition. Some will say preignition won’t happen because of the knock sensor. They would be wrong. The timing will adjust but not instantly and not just occasionally when the hv battery is very low. Signs of a bad hv battery include fast discharge at a stop light, particularly with the AC compressor on, requiring the engine to start. The hg rattle is a much more violent metal to metal sound independent of hv battery charge or octane. Pinging is a higher frequency noise kind of like a loose heat shield vibrating. Any old school mechanic will recognize pinging but the same guy will think you have ruined the engine with a hg rattle.
Are you positive the rattle comes from the engine and not from other source like for example corroded and loose heat shield(s) around exhaust assembly?
Are you positive the rattle comes from the engine and not from other source like for example corroded and loose heat shield(s) around exhaust assembly? Also I would get/borrow some scanner to see what is going on with engine ignition system, many affordable scanners nowadays can monitor live stream data so you could look up their menu and find parameters and sensors related to ignition system and see if there is anything abnormal going on. I got myself a $50 scanner which reads live data and sends it to cellphone app from every system and each sensor in the car and it helped me to diagnose intermittent faults in one wheel bearing sensor that was causing ABS and TCS systems to go into a limp mode.
