Prius cold engine knock poll

Got it this past weekend. Started the car up (it was cold) and started backing out of the driveway. Engine turned on and shook about 2 seconds before smoothing out.

 

Only had this happen one time. It sounded horrible. Like most everyone in the thread you linked, I had moved the car a very short distance (< 30')the day before without a proper warmup.

 

This just happened to me. Car was driven normally then parked for four days. It was a pleasant spring morning - not too cold. Started up and heard loud engine knocking for around 4 seconds before it went away. Very worrying. It has not happened since resuming regular driving. I asked my Toyota service department to log the incident. I am hoping there might be a fix or recall in future under powertrain warranty.

 

not to worry, it happens to a lot of people, doesn't hurt anything, and is unfixable. try not to shut it down while the ice is running.

 

It has happened to me three times; all during cold mornings following moving the car a short distance the day before. As nasty as the knock sounds, I'm not too worried about as it seems to be very common.

 

stop moving your car!

 

Engine knocking and shaking just happened to me again after starting up having driven half a block only to move my car beforehand. Temporarily resolved when applying gas but returned again immediately. Please report these incidents to Toyota. This is not normal.

 

not normal, but so common, most have learned to live with it, or avoid it.

 

If it's not normal (which it isn't) - it should be reported. Whether it's misfiring or moisture, Toyota needs to address it. Even if this is only happening every few months, it cannot be good for the engine long term. It has happened to me even when waiting for the ICE to stop running. It seems to be that very short trips and the angle of the car (whether parked on a slope) might be factors that contribute to the knocking.

 

You need to let it run and only turn it off once the ICE shuts down. The ICE has to warm up, it takes about two minutes. Do this and it will not happen again. It's a non-issue, caused by driver error. Remember this is not a normal car and can't be driven like a normal car.

 

Driver error? I disagree. Unless the manual advises against interrupting the ICE on warmup?

Anyway, I noticed this on the 2010 Gen 3 liftback...as a result of the ensuing anxiety it caused and with the dealership unwilling to implement the supposed fix, I "upgraded" to the 2012 c. I *may* have noticed a slightly rougher start on occasion when recreating the required conditions in this vehicle, but it was nothing as severe as the liftback. As a result, I've been able to put it out of mind, but it sounds like some folks above are having the more violent knocking that I witnessed on the Liftback. I can't blame these folks for their dissatisfaction at all. The surefire way to prevent it is to not interrupt an ICE warmup, but that's a bit wasteful if you're only moving the vehicle a matter of feet. The other expensive solution is to upgrade to another vehicle altogether.

 

The warm up is less then a minute during summer, maybe 3 or 4 minutes during winter, hardly wasteful.....or just don't move it around.

 

They could minimize the problem by allowing EV operation for those very short-distance moves, assuming adequate charge, etc.

 

yes they could. do you think we'll get it on the gen IV?

 

I'm actually able to use EV mode to move it without issue in the warmer months. Running the ICE for a few minutes in such a scenario may only be minimally wasteful, but it also contributes to further wear and tear. It's also why my next vehicle is likely to be a BEV or PHEV.

You can switch to EV mode now actually if certain variables are met (high enough ambient temperature, adequate battery charge as you postulated, etc.). During the winter, forget about it (unless your garage is well heated).

 

I made the mistake of moving my 2015 Prius C Two to a different parking spot on our two-lane driveway, and cut off the engine while it was warming up. Big mistake!!!

Here is the sequence of events:

Friday: back and forth to work as normal (90% highway for ~65 miles), plus a small amount of low-speed cruising around town for errands, but nothing out of the ordinary. Temps in the 80s F.

Saturday: started up to back out of driveway and move to another parking space. I believe it is in what the Gen3 startup thread calls "S1a" (or possibly S1b, though it wasn't on that long) when I turned the hybrid system off. Temp was maybe 92 F in the sun (which the car was for most of the day). Hot day.

There it sat, until Monday morning. when I was going to work mid-morning. The first several hundred turns of the crankshaft yielded what sounded like terrible knocking and grinding noises. Lots and lots and lots of misfires, maybe 50-80% of cylinder strokes were audibly misfiring. I can't tell if they were early ignition, late, or what... but the knock sensor seems to have worked, as you could hear that, as it started pulling the timings, the knocks became less and less frequent. By the time S1a was complete and the engine started to rev up a bit more for S1b, the knocks were basically gone. At that point, I started driving, and by the time I hit S3, there was no knocking. Temps were in the upper 80s.

Then, on Monday night, Tuesday morning and Tuesday night, I got way fewer but still audible knocks during the first few revs of S1a. Maybe 1-5% of the revs were knocks, and they were a few seconds apart each.

Oddly enough, the knocks have completely disappeared or are so minor as to be unnoticeable, for four cold starts of my car (Wednesday morning and night, and today morning and night).

Seems like it's similar to what happens when water gets in your windpipe. You cough real hard for a few seconds, then for several minutes after, you feel like you could cough more, until you finally get rid of it, but it's pretty persistent.

Wondering if I should take it into the dealer...

 

No dealer needed, just allow the car to warm up and shut down the ICE before turning off the car. You should not experience this again. I also use 91 Premium fuel, not sure if this does anything to help or not. I have 42,000 miles and have not experienced it in the last 40,000 miles.