Mileage at time of problem detection: 373,991 miles.

So most of you have probably heard or even experienced the dreaded violent engine vibration. I've had it happen on my 2012 Prius C, my 2014 CT, and even a 3rd gen Prius I once rented while my CT was in the shop. It happens to many of the Prius engines apparently. Well, in my 4 years of ownership, I've had it happen on my CT about 6 or 7 times. Three of those were in the last 2 weeks or so.

Tonight, I had the third one happen, but this time, it was followed by a check engine light. This will be my first check engine light since buying the car new. I will be going to the shop on Monday to see what's going on, and will update once I find out what's going on.

 

Small update:

Dropped by my mechanic's shop today. He was out, but they took a look with their scanner. Engine error codes 302 and 304, I believe. Cylinders 2 and 4 are misfiring. There is a recent TSB for 2014-2016 CTs for this. It calls for reprogramming the ECM to use new software that "reduces the possibility" of this happening after a "cold soak."

Will be setting up an appointment soon to get this taken care of. I can confirm that the violent shuddering/shaking/vibration is happening EVERY time the engine cools down, even while driving.

 

I thought those cold soak are really cold meaning freezing or lower? What temperature are we talking about?

 

I've had them happen in all sorts of temperatures. From 30s all the way to 70s. I think cold soak might just mean the engine has been off for a long time (like overnight). It was in the 40s / 50s the night this specific case started.

 

as always, thanks for your continued input!

best of luck

 

No problem at all!

Small update: My car's at the shop now, for an extended stay while my mechanic checks to see if anything else is up with the car that could cause this issue. The main thing though, is that as of yesterday, the problem got worse. Not only was the misfiring happening every time I started the car after the engine cooled down enough, but now it's EVERY time, period. This means even on the highway, when I slow down due to traffic enough to go into EV mode, and then pick up my speed 3 seconds later and the engine kicks back in, it does it.

Waiting on word from the shop then will update again.

 

Hope you get it figured out. Not saying its done, but almost 375k miles before a potentially major issue is still very impressive

 

When was the last time plugs and coil packs were changed out

 

Never changed coil packs. Spark plugs were last changed at 260k.

 

Major update:

My mechanic decided to open up the engine (took the valve cover off), curious to see what's going on before tackling the issue (in case there's another reason for what's happening):




He found a few bad signs...

1. There's a strange milky white / tan gunk on the inside of the valve cover that he's never seen or heard of before (it turned out to be coolant mixed in with the oil):



2. Anti-freeze has made it into the throttle body:




3. Scoring on the camshafts (debris in oil):




And 4. The original issue: darkened spark plug from bad combustion due to low compression (note, these are OEM plugs):



He's researching how coolant and anti-freeze leaked like this (compression test is next). Also, why Lexus has a TSB to replace the intake manifold for the compression and misfiring issue on the 2011-2013 CTs, while only an engine management software update for the 2014+ models is called for (Toyota / Lexus doesn't say why, they just cite this to be done).

He recommended rolling back my OCI (oil change intervals) to 10k or 15k, instead of my current 25k, so that any issues like this don't sit and worsen over time inside the engine block (like debris and coolant leaks). It will cost me around $400 to $500 a year but it's worth it to keep the Courier CT running for a long time.

Looks like my CT will be out of action for a while. Good thing my mechanic has his own loaners.

 

I'm not a mechanic by any means, but it sounds like head gasket failure:

https://en.wikipedia.org/wiki/Head_gasket


Best of luck.

 

I looked at the link, and yeah, it does look like a head gasket would be responsible for all of this, except for the throttle body stuff. My throttle body was cleaned two times by my Lexus dealer through one of their "routine services."
​​​​​​
I wonder if they didn't seal it properly when they put it back that last time they did this.

 

I had a small "shake" today, and a few days ago, and I thought about your post/this thread. I'm in San Diego so, cold weather does not exist here. At this point I am wondering if that TSB is something that is affecting my 2013 CT.

NOTED:
A dip stick check did reveal that I was low on oil, below the lower tick/marker. I did top off a quart ... Lets see what happens over the next few days. Fingers crossed..... for teh both of us

 

How often do you check the oil dipstick? I make it a point to check whenever I gas up. It only takes about 2 minutes or less.

Also when the engine is COLD, unscrew the coolant reservior plastic cap and see if there is any "strawberry foaming shake appearance stuff" (BAD) and to look at the coolant level (should be between low and high). Also with the engine COLD preferred, unscrew the engine fill cap and examine it to see if the same foaming (BAD) is present. IF there is foaming present, this indicated you have coolant mixed up with your engine oil which usually does not end well.

 

honestly, never .... up until this most recent 110k oil change. after every oil change I always pour used oil from the oil drip pan back into the empty mobil 1 container. usually 3.5 qt's pour back, this time only 1 qt came out and I knew something was wrong. I now check every 1k and I do see consumption, and I have to top off a qt every 2k ish. since then, I did replace spark plugs and pcv, so I am hoping that will slow down the oil consumption, time will tell.

I unscrewed 2 plastic caps that contain a pink fluid, 1 by the passenger head light and 1 on the drivers side by the brake fluid reservoir. in both cases, no foam/anythign that resembles delicious milkshake. I also checked the bottom of the engine fill cap as well, and no foam.