Brand new Prius, deep knocking on start up

Knocking on start up is usually from misfiring. Buy a $20 OBDII scanner and scan that car. See the code pulled. Although unlikely, there is a chance that it may have something to do with head gasket. You don't want to mess around with that. Since it's only 5K, the warranty should still be active. Go to dealership ASAP.


There are many potential causes: bad spark plugs, bad coils, bad harness, head gasket, etc..

See if your coolant is going down but it's not dripping down the ground. If it does, there's a high chance of it being head gasket issue.
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Take it to the dealer.

BUT - try turning the Climate Control OFF before starting and see if it's the same (If you've got enough battery, the engine probably won't start) - then flick the accelerator enough to get the engine to fire - does it still make the noise? Then turn on the Climate Control - any noise then?

 

I often hear noises that sound like the engine is running rough and is about to lug, while it's still warming up - I believe in S3a stage transition - but no knocking. See The Five Stages of Prius Hybrid Operation "The Stages" paragraph "S3".

 

Generally, when I start in the morning cold, I've got Climate Control OFF - and the engine doesn't start. In the estate where my home is, I generally get out of my street in EV mode, but as I accelerate in the next street, the engine kicks in - and, like any engine starting cold, is a b it rough for a second or 2. It's accentuated because of the relative silence leading up to that point.

 

its probably the new normal for toyota engineering. try another new one at the dealer

 

Turning the car off whilst the ICE is still running tends to create this, especially if it's turned off during the warm up cycles, caused by excess fuel in the manifold.

 

Both priuses that I've had have done that at least once, but not regularly.

 

is this still happening in gen 4?

 

Not had it on my Gen 4

 

Mine (16 Prius) Just started doing this, similar to my coworkers corolla. Maybe done it a handful of times earlier than approaching this mileage but I notice it once every two weeks and usually almost always on a cold startup.

 

Same with mine since new and it's more pronounced when it's cold out. I think it's normal characteristic of this engine and you might be able to reduce that noise using fully synthetic low viscosity oil .

 

Nah, that can't be.

In Initial Post video, it's just for a split-second, around the 5 second mark, not the protracted slam-slam-slam of longer-in-the-tooth third gen, but still: not good to hear.

 

I had this knock and difficult starting with a 1995 Ford Mondeo years ago, so I wouldn't say it's a characteristic of this engine. More a characteristic of how it's treated, turning it off during the cold start cycle for example. My Gen 4 has never done it, maybe coincidence but I believe it's because I never turn the car off whilst the ICE is running, even when hot. I let it finish it's current cycle, whether it's the warm up or just topping up the HV battery. If it happens to be warming up the cabin I turn the climate off, then the ICE shuts down.

 

FWIW......I've had my Gen 4 do it a couple times......very lightly & WITHOUT the mis/fire associated with the Gen 3......

 

I brought new 2020 Prius last September, after couple thousand miles, I noticed very deep clicking sound from right part of the engine when I start car in the morning and also smell burning oil from exhaust, like old engines will smell, what is this? This is my second Prius, I had to sell it at 150k miles due to the loud rattling sound from engine, but this is brand new car, why it smells like old one, I need go see the dealer,any one had same issue? Any suggestions how to convince dealer to really take serious look?