Motor shakes when it first starts up or takes off

The Prius Gen III cold start knock can be duplicated by:

1. Drive the car long enough to get the engine completely warmed up
2. Park the car outside at 50 degrees F or lower for 8 hours (get engine stone cold)
3. Start and run the engine for 10 seconds and then shut it off
4. Let the car sit for at least 4 hours, preferably overnight
5. Start the car and you should get a few seconds of engine knock.

This knock condition does not last for minutes, it lasts for at most 15 seconds while the engine is idling. You may be able to experiment and shorten soaks times.

 

this just happend to me and my 2010 Prius this morning and I live in Arizona. I had driven it earlier then parked it for about 4 hrs..started it up and it started shaking...turned it off, started it up..same thing. Ran it for about a minute then it seemed fine. Too freaked to drive it. Came to the chat room and see that it is a problem reported, so will drive it home and call the dealership to see if they have a solution yet. thank you chat room!

 

I've had the same vibration problem with my Prius c. Scared me to death the first time, lasted about 15 seconds and stopped to run normally. The second time the shaking was not as violent but the noise was there. I took it in for its 10K service and asked them to look at this and another problem I'm having with the audio system. He told me that they did diagnostics for the electrical and audio system and it checked out normal. Then he went on to discuss the slight vibration that is evident with the car switches from the electric motor to the gas motor, as if this the problem I was reporting. I cut him off, told him that I know what the normal sounds are and what is occurring is not normal. It didn't happen for them so I'm in the same boat. I live in Southern California. My car is garaged overnight and garaged at my work. The car is never getting that cold.

 

I get the vibe also.

 

I now have 3,300 miles on my C4 and it did the engine shake and rattle for the first time on Saturday. The car was driven for 4.5 miles on Thursday evening (44 °F and dew point of 36 °F). It sat in an unheated garage for 36 hours at 48 °F. On Saturday at 11:00 AM I moved the can into the driveway and the engine ran 5 to 10 seconds before it was shut off (sunny 36 °F with dew point of 29 °F). When the engine started 5 hours later, it shook quite a bit and the loud "rattle" noise was obvious for about 15 seconds. This shake and rattle was just like what I used to get on my 2010 Prius liftback.

The prescription for causing the problem is the same for the C as with the liftback. Start a cold engine and only let it run for 5 to 10 seconds and then shut it off. When restarted 5 hours later (or longer), the shake and rattle occurs.

If Toyota is correct that "condensation" in the intake manifold is causing the problem, then the condensation is not water condensation from air entering the air cleaner from the outside. You cannot create any significant condensation in the intake in 5 seconds. I suspicion that the "condensation" is from water vapor and unburned fuel that escapes into the intake manifold during 5 or 10 seconds of engine run time when the engine is cold. The Prius has an Atkinson cycle engine which means that the intake valves stay open after the pistons begin a compression stroke. It is possible that unburned fuel (the engine is running rich during warm up) along with water vapor from the fuel burn is going back into the intake manifold where it condenses. When the engine is restarted hours later, this condensation mixture is auto igniting before top dead center (dieseling) causing the violent "shake and rattle'. Once the intake manifold cleans out, the engine settles down and runs fine.

 

When this first happened to my wifes 2012 prius with under 20,000 miles on it, I thought because the car starts in the electric mode and switches to the engine that it is a transition problem from the electric system to the combustion engine. After ready a bunch of chat sites and this post I am not sure what the problem is. The issue I have with this cold start theory is that people in warm and even hot climates like Arizona and Cali have the same issues. However Dick has explained something that I didn't know about the intake valves staying open. If you would, could you explain this a little bit more. I don't understand why the intake valve says open during compression. Doesn't this go against everything about the way a cumbustion engine works.
Thanks

 

What happens if the second you hear the noise you shut the car off. Wait 20 seconds and re-start the car?

 

In an Atkinson cycle engine, the intake valve can stay open longer allowing air entering the cylinder to go back into the intake manifold. This results in the compression ratio being smaller than the expansion ratio. The goal in an Atkinson cycle engine is to have the cylinder pressure at the end of the compression stroke to be about atmospheric pressure. Engine efficiency is maximized at the expense of hp per displacement (power density). You can look this up on Wikipedia. My point in all of this is that the exhaust of air in a cylinder into the intake plenum could result in the condensation that results in the "shake and rattle" at engine start up.

 

Mine does it every cold start-up, done it from the day I picked it up at the stealership. Sometimes louder than others, sometimes does it longer than others. I figure its normal for the C. Just like the gurgling sounds my Silverado makes swilling fuel.

 

Hello. I have had shake a few times also. This morning it was really bad. I didn't use the car all weekend and when I got in it to go to work and started it the car had a bad shake for a few. Didn't time it but it goes away soon after. No lights on dash and no stall. I'm sure eventually after enough complaints toyota will issue recall.

 

Question for the people having this problem: Are you using Toyota 0W-20, or are you using some other oil?

This sounds like cam phaser (variable valve timing sprocket) slap, and it's pretty common on four cylinder VVT engines in cold weather. What happens is oil flow isn't high enough through the control valve and into the cam phaser, so adequate pressure isn't kept on the vane. As the intake cam rotates (at idle speed) and starts to compress the valve spring, the vane in the phaser is at it's mechanical stop inside the housing. As the cam lobe passes it's lobe center, valve spring pressure pushes the cam forward, and if the pocket in the phaser isn't kept full of oil, the vane and cam will snap forward.

This is easily verified on a scope comparing CKP to CMP. Of course, that would mean the dealer tech would have to know how to use a scope and , god forbid, know how to interpret the wave form.

Most modern cars do this a little at idle, but it may or may not be audible, depending on the amount of oil in the phaser at idle, and of course the amount of sweep in the phaser. The Prius VVT has a lot of sweep, so a lot of room to move and make noise.

The CMP sensor reads the cam position on the rising edge, which is always on the lift side of the cam lobe, and therefore, always in time as the PCM sees it. Therefore, no code is set.

If this is what's going on here (which is what it sounds like), it likely won't harm the engine.

Suzuki uses a pin that holds the phaser in place until adequate oil pressure pushes the pin out and allows the phaser to adjust. While this eliminates the slap problem, These phasers break (cost a lot of money to replace), and Toyota's don't.

There is a TSB 0010-12 for the symptoms you describe, but only for the 2010-2011 Prius. There is no TSB for the C.

Cheers,
Matt

 

I've got a Prius C that's done 6,000 kms and it did it to me this afternoon after a couple of days not being used. We are in New Zealand and the temp today was around 70F so not cold related. I was aware of this problem in earlier models and i'ts a shame to see it haunting the new ones too.

 

try using a 98 octane fuel for a tank or two, i've taken my car to the snowys and i know that e10 @ 91 octane fuel has a problem with condensation, so every fourth tank i get 98 and i have had no knocks since.

 

You maybe onto something. I always ran it on 98 until a few months ago when I was told it didn't improve performance at all unlike the advice from a salesman at West Toyota. Still a shame to have to put dear gas in when the Prius is about saving money on fuel ... Oh yes and the environment too. Still a very cheap car to run.

 

Nope, it's just a misfire. Here is how you can duplicate it in your own car:

 

the reason I put 98 in is to keep the system clean.

Today tonight did a thing on all the fuel types available and e10 won by 50km followed by 98

In other words they are basically the same but 98 is mixed with fuel additives to keep the system clean

 

I've always gotten worse gas mileage with E10. It's usually about 10%... or it was in my Saturn. I haven't had enough fill ups with the two types to track in my PC.

 

i looked up the report and got some numbers mixed up however my conclusion is the same e10 wins distance per dollar and 98 wins distance per L

 

Well then maybe my Saturn just hated the mixed stuff, because I could always tell when I wasn't using it. My range would improve by around 40 miles per tank when it wasn't E10.