Engine shaking badly at startup

Very concerned You have a blown head gasket which should require an engine replacement so beware of trying to fix it It will be costly and you could need the main reciprocating mass of the engine replaced which is about a 1900 assembly plus the cost to install it and all of that this is an open deck design engine It is inherently weaker than some other designs It can rattle itself into broken parts so any parts reused from your assembly should be magnaflux and checked for cracks and damage as it is very easy to occur If the car really is in that good of shape no blown outdoor panels armrest caving in in the doors so on and so forth and you really like the car You could fix it with a JDM spec engine or an engine built here in the United States for around $5,600 or so that is a choice you would have to make It's a choice I would not make and would not do personally I've done it once it was not worth it for this particular generation of this car but those are choices an individual has to make Good luck and really consider would this be something to do or would just picking up a Yaris or a Corolla be a better option for you Do you drive enough to notice the savings seems like with the car sitting for 5 days maybe not Prius do not do well sitting a Yaris or a Corolla can sit for months so there's always that the difference between the Yaris and the Prius and gas mileage is extremely minimal May not be worth it to have the battery and the electric motors in the transmission if they're not being used a lot or like they're supposed to.

 

What’s the miles on it?
How’s the coolant level?
EGR and intake manifold ever been cleaned?

 

Don’t assume they’re pretending.

That would be best. If it’s the head gasket, the engine shake is usually due to coolant in combustion chamber. Piston struggles to get over TDC in a cylinder with the (incompressible) coolant. Eventually something gives, either bent piston arm, or broken damper twixt transaxle and engine.

boroscope inspection and leak down test are the main diagnostics.

 

If this is just started it is possible you could save the engine but still it's going to be 3:00 to 4 grand to do the saving You can get another engine from the Japan domestic market that is like 70,000 mi on it for $1,300 sitting at your door or you could have I don't know what the prices are at the moment that's what I paid and that should be able to be installed in the car from a local person that knows how to install engines or four or five in my area I paid like $450 I provided the oil the red Asian coolant and any other liquids new spark plugs and what have you to the mechanic I even had to undo the hybrid safety plug for him and he swapped out the engine assembly with no problem just as if it was a Corolla and he was able to put everything back just like you took it apart then I came and put the plug in backed it out drove it away Not anywhere near 5 grand The car is just not worth that at least not to myself.

 

Looks like the shudder from 2021 has shown itself as engine rather than AC compressor.

Toyota and their mechanics do not believe the egr - head gasket theory. If it clogs and codes they will recommend new parts, if the egr valve sticks they want to replace the valve.

The hg leak fouls the spark plug and clears quickly allowing the engine to run smooth. If allowed to progress for months, the leak no longer seals up quickly and may then lose coolant and worse case, can hydrolock.

Options
Clean everything still knock when pressing on gas pedal | Page 2 | PriusChat

Hopefully the brake lights are not still on. If so repairs may be sccumulating.

 

Typical failure is coolant leaking into cylinders. Usually at the wall between cylinders one and two.

 

This link shows the different types of head gasket failure that are possible.

From my study, the most common failure seen in the Prius 1.8L engine is between combustion chamber and coolant passages, illustrated as type 6 in that diagram.

Oil-to-coolant breaches (shown as type 4) appear to be a lot less common.

 

more likely its condensation build up in the inlet manifold which causes the engine to shake on startup

 

It's also possible that the head gasket hasn't failed yet, especially if coolant level is constant, and if such shaking incidents remain rare. Prii have been exhibiting this alarming behavior occasionally since before head gasket failure was a thing. It happens when a dollop of condensed water from EGR (or PCV?) finds its way into a cylinder at startup.

Even if your head gasket isn't at fault this time, 183K miles is past time to check out the EGR flow and clean out the manifold EGR passages if that hasn't been done.

 

Just throwing it out there- ignition misfire? How old are the spark plugs?

 

^this. Cleaning the EGR late in the day doesn’t cancel the effects of protracted run time near-clogged.

 

Last winter, I experienced a few times (around 2-3) something similar at start up. The engine was shaking and noisy- not violently, but enough for me to notice there was something wrong. It happened to occur on mornings that were extra cold in temperature. After around 30 seconds, the shaking stopped and I forgot about it. There's no issue with coolant level.

It hasn't happened this winter yet, but a cold spell is coming this weekend. How common in this and does my example indicate HG issues, too?

(115k miles and plan on changing spark plugs soon, original fuel pump)

 

EGR cleaned?

 

If it is happening once-in-a-blue-moon rather than consistently, associated with sitting shut off for a while in cold weather, and especially if the last run of the engine before sitting was too brief for it to warm up, then yes, those are the symptoms of the water-snort-from-manifold business, the one identified in T-SB-0010-12, not a head gasket problem at all. To make it less likely, avoid brief no-warmup engine runs when you're about to let it sit in cold weather for a while.

But if it happens every time the car has sat long enough after you last used it ... or if there's any funny business with the coolant level ... those, then, would be more the signs of a head gasket.

 

The "snort" is real, but with 115K you don't want to relax just yet; clean that EGR.

 

Yes, cleaned via the service provided at Hybrid Pit in Orange County.

 

Just recently? Hopefully dodged you-know-what.