Hi,
Been using lexus CT 200h for about 2 years now. Recently I've noticed some weird engine shaking when driving at low rpm (exactly when speedometer hand is in a middle of ECO zone). Lexus dealer says everything is alrihgt. There are not engine failures etc. It happens mostly when the engine is cold, or is noticeable when driving uphill.

Has anyone come across a solution? Been searching the web but with no results.

 

These drivetrains tend to have a bit shake when transitioning between the engine and electric motor. There's sets of planetary gears to allow multiple power input sources, and no real mechanical way of keeping them locked/isolated when not directly in use. So there's always going to be some degree of driveline shake. Now, if your engine is *actually* running rough even while idling, then you may have to dig deeper.

I'd recommend doing an intake manifold clean, EGR valve/pipe/cooler service as this is always smart on these engines and don't be afraid to drive briskly to clean out some of the carbon (disclaimer: always drive safe).

The engine will also go into a higher rpm/load demand mode when you bring the HV battery into a low state of charge..last bar remaining on the dash gauge (think: stop and go traffic in electric mode with the A/C on lots) as it serves to bring the state of charge back up quickly.

 

It sounds like your headgasket is going bad. It's an extremely common issue on these cars, exactly with the symptoms you describe. It's especially noticeable every time the engine comes on (like in the middle of the eco range) while it's cold and not warmed up yet. The EGR system is clogged and the headgasket can't handle the pressure and blows out, causing oil and coolant to mix and flood the spark plugs. it will get worse, and you'll eventually get misfire check engine light codes.

 

Hopefully not but you make a valid point! @Martinez8282 I'd start with buying a Head Gasket Combustion Leak Test Kit to analyze whether or not your coolant has combustion gases in it, you definitely want to try and catch this one early.