Shaking when ICE kicks in

I have a 2017 prius with about 42k miles on it. My wife drove it through a puddle about a couple of months ago. The engine light came on. I was traveling so I asked her to park the prius and drive the other car. When I got back 10 days later I could feel moisture in the floor mats and the check engine light was on. I started the car and drove it about 50 miles and the engine light went away. However, I could feel a shudder/shake everytime the engine would kick in especially if you keep a light foot on the gas.. With a light foot it is a sustained shake. If you accelerate hard, the shake goes away. There is zero shake whe the car is running on electric motor. I have also notices that the shake is minimal when the car is cold. The translation from ICE to electric and back is smooth. I took the car to a local garage. The plugs got replaced, coils are also fine, air filter replaced. They even opened the inspected the transmission damper but no issues were detected. There are no error messages when you put the scanner in. Any idea what might be the cause? Thanks

 

Steady no visible loss over the last 2 months

Steady level. Have observed no reduction.. tx

Coolant level steady and no reduction observed.

 

Thank you. Have checked plugs, coils and all relevant sensors still the same. As a last resort, am have the ecm looked at for potential transistor misbehavior. Will update ASAP. Thank you for your inputs

 

Adeendum: The shaking clearly is on account of engine misfiring at low rpms.. unfortunately it is at the sweet spot where all the gas savings are. If you keep rpms high misfiring disappears ....will update soon. Thanks again

 

Hello folks. A very late update. We tried everything but the shaking persisted. About 2 days ago my mechanic closed the airflow for the egr valve and viola the shaking/misfiring disapperead. The car is at 62k miles now. while it's a relief but I am thinking driving with the egr feedback pipe blocked might cause some long term issues? Also since blocking this pipe has solved the problem for now, what do you think the permanent fix could be? Is there some.egr sensor or something that might need replacment? Tx

 

We have run multiple scan ls but no errors at all. Stopping exhaust gasses from being fed back has solved the problem somehow. Want a permanent fix as now inclined to sell the car and don't want to sell the car to a new potential buyer before solving this issue first. Coils, plugs etc all had been replaced not too long ago.

 

Thank you. Will try the fix you recommended and report back.

Service intervals are regular and I use the recommended grade Motul oil, so decent quality.

My wife had driven through a pool of rain water some 2 years ago when this problem started. Could that have caused it?

 

Thank ypu.

Changed the EGR valve and issue resolved. Took almost 2 years to get to this. But thank God back to driving like a dream. Thanks.for everybody's input.
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