As I was picking up my McDonalds order (consisting of a single $1 soda, because I am a Prius Prime driver and of course I would have a $1.09 order) my car transitioned from EV to ICE mode as the harried worker swiftly swapped soda syrups. I cringed, knowing that my hard earned dollars were now being pumped into the Gasman’s pockets. My, what a clatter! It sounded like my old Jetta TDI when cold as it spun the ICE to life for the first time that day. I thought my lovely car had right shit itself, but no codes. It quieted down after 2-3 seconds and remained quiet despite cycling on and off a dozen times or so as I returned home. Any idea on this one y’all? 21 Prime LE, 15,542mi
Just to be clear, are you saying that your ICE has never come on in the 15.5K miles you have driven the car? I am guessing that the valve lifters were dry for the first two seconds. 17 Prime Advanced 19,900 miles
Probably one of your plugs was fouled causing a short misfire. When that happens the usually inactive clutch damper between the engine and transaxle slips due to a lack of sync between the engine rpm and the planetary gears. It makes a metal to metal racket.
Is there anything I need to do to rectify that situation? I can't believe I'd have to replace my plugs already... I've seen a video of that - doesn't it continue for awhile, or as long as the engine is on? This only happened for 2-3 seconds and then it was fine.
At 15,542 miles, I doubt it is caused by anything worn or fouled. The first few revs of a cold-started engine just aren't super smooth every time. That's been true as long as there've been gasoline engines, but in a Prius the sound is extra clattery because of the way the transmission works. If you have Techstream (and haven't made too many other trips since that one), you could pull up the misfire monitor and see if it counted any. (Many non-Techstream scan tools can probably do that too.)
Maybe a cautionary tale? Toyota doesn’t really weigh in on this, but it just might be a good idea, use the car in hybrid mode (engine cycling on-off) semi-regularly, say once a week?
Welcome to the world of "WHAT IS THAT NOISE!" My 2021Prius also makes some strange noises when the car turns on the gas engine. We have to remember we have a lot of electrical things that the old cars don't have. (We have no starter, no serpentine belt, and no alternator.) We even have two sets of brakes, the old car brakes and the regenerative brakes. (The regen brakes prime themselves often and is that strange noise we hear when the car is cold and we open the door.) You may have, also, heard the infamous "UFO" sound when driving slow. (It's supposed to turn off when the engine runs but mine sure doesn't) So relax and only sweat stuff if the car pops a "check engine" light...there's something like 53 computers so it will let us know if something is wrong.
Yes, for example when I've got the A/C on, charge is at --%, and I'm chilling in the car. Engine comes on then - you can definitely hear it start, but this was a straight up rattle I've never heard before. I hope so. I've heard it start many, many times and it's just never been this loud before. No Techstream unfortunately Good point but I run the car in hybrid mode almost every day. I drive *a lot*. Totally, and that's valid - but I'm intimately familiar with the weird Prius noises at this point after putting on almost 16k miles in 4.5 months. Unfortunately this wasn't a fun sound, it was absolutely not normal - sounded like a clanking rattle I think you're right that I will just wait until I see a code/MIL pop up.
If you can get it to repeat those sounds, try to get a video recording of it with your phone. You could upload it onto youtube and have folks here listen (and even have a Toyota Technician listen to it....we all know cars never make the same sounds when a mechanic is there, little buggers!)
The gen3 rattle is also short term and clears as soon the pistons pull more fuel air in and the plug fires. In the case of a gen3, it is often serious, because there are a lot of head gasket issues where coolant is seeping past the head gasket temporarily fouling the plug. This creates a very loud and somewhat violent shaking that does clear up in a few seconds. Something that will make you say Holy ****, what was that noise? Something that is clearly not the brake pump, low speed warning, typical valve noise, fan noise - eg a loud and damaging sort of clatter. There are other ways to foul a plug or cause a misfire. Condensation and oil from the pcv, leaking injector pooling fuel, bad plug leaking through through its insulator, bad valve seal, bad coil failing to immediately fire etc. I would only seriously worry about it if it repeats.
Thanks for the info and reply! So the Gen 3 rattle doesn't just clear up by itself, you'll hear it repeatedly, right? If so, I agree that I'll try to forget about it this time and then proceed to freaking out only if I hear it again.
The gen3 clears itself after a few seconds and typically does not happen after it warms up. It may not rattle everytime when cold, likely due to the position of the cylinder and valves. Some go weeks or longer between rattles even when time proves it was a head gasket. Because of the typical slow initiation of symptoms, the coolant reservoir level does not appear to be changing. Once a gen3 is really bad, the cold start rattle will be more consistent, the coolant level change is obvious, all the auxiliary plug/coil/injector/egr parts are changed/cleaned only to finally confirm white smoke out the exhaust. All that is a gen3 hg fail with a typically slow leak. Occasionally we see a loose head bolt or a severe overheat which often causes a more immediate and obvious hg failure.
There's also the "stopped/moving slowly, open window, next to a brick wall" strange noise phenomenon. I have heard strange new noises from my car when I'm moving slowly/stopped, next to a brick wall (or other large, flat solid object) with my window open because the car's noises are bouncing off the wall into the open window. Usually, it's squeaky breaks (not in the Prius), but this is often the environment where I either normal sounds in a new and different way, or unusual sounds that point to trouble down the road. I agree, if you don't hear it again, you can probably forget about it.
