Thoughts on engine shaking

In general shuddering when the engine is cold is a normal quirk of Prius engine design... Shuddering when the engine is at normal operating temperature could be a sign of a blown headgasket or some other engine problem. LEt us know more and we'll walk your through your options.

 

Motor mounts?

 

Head gasket problems seem to be uncommon on the Gen2 1.5L. Keeping an eye on your fluid levels and conditions is always a good idea.
Quick thought, does your CEL come on as a bulb test when you power the car up? I have seen some folks try to disable or cover up the CEL instead of fixing the problem that triggered it. If there is an engine misfire, it is often accompanied by a rattle or knocking sound under light ICE load as the uneven engine speed causes the dampener between the engine and trans to hit its full travel limits- hard.

The engine mounts are fairly conventional, two up high, (one at either end of the engine and transmission), holding up all the weight, with a third "dogbone" underneath controlling torque wrap up. They can "collapse" some (compress) as they get older and transmit engine vibration through to the body. Not too often but sometimes. If I replace them I only use OE parts- the aftermarket stuff is garbage for this.

 

Yea motor mounts are an issue with big powerful engines... Not so much with these little guys...

 

On the Gen 2, there is a point in the warm up process where the ICE will give a little shudder off & on while stopped. To me, it felt like the car behind me had just barely bumped my bumper. This article explains the stages in a 2nd generation Prius.
http://techno-fandom.org/~hobbit/cars/five-stages.txt

 

Cant be too bad if no dash lights. But Time to get involved.

Your car is over due for new spark plugs probably needs a new air filter and the throttle body cleaned. The pcv valve could use a change and its 2 hoses may have cracked ends mine were cracked at 110,000.
Def needs a new water pump belt.

Then it could use a trans fluid change and an inverter coolant change and a ICE coolant change but for that I would just dump the rad a few times so as not to invoke the dreaded G2 airlock.

Clean the front ac condenser and service the ac ecoil under the dash next time the front end of the car is in the air.

Use a new factory oil filter and 3.8 quarts of Mobil One 5-30.

 

Oh good got the belt done. That stupid design no temp sensor will ruin your day.

Did the engine have this issue before you changed the plugs or it started after the plug change?

Did you look in the plug well before pulling the plugs for an oil leak that’s really common on this car and most four bangers the gasket leaks around the plug wells eventually. To bad because valve cover gasket is easy if your doing the plugs as you are in that area.

 

Easiest way to inspect the wells during spark plug changes is with your phone camera...

 

I tried the phone but when you get close to the hole it was too dark. I didn't try much as I had my lighted bore-scope but it proabaly would work ok.

 

No cel so its strictly mechanical which is good. Your plugs and cops and injectors are ok or it would throw a misfire cel real fast otherwise.

Seen a bunch of broken motor mounts lately on this site.

Go on YouTube and search PRIUS INSPECTION.

It will show you the chicken dance to put the engine in inspection mode and engine will idle continuously till you shut the car off. Give it a good looksee while its idling.

Jack up the front a little and get under there while its running and listen to the engine and look closely at the front and back motor mounts for movement. You may see why its shuddering.

Good Luck.

 

if you put your camera in video mode it will turn the flash on so you can see...

 

I had some engine shaking a few years ago and it was my ignition coils going out. I ended up needing to replace a couple of them and everything was back to normal.