IrishJoe

My 2017 Lexus RX450h is four weeks old. I've driven it at least once every day, and it has been smooth as silk most of the time. However, five times when I've started the engine, it has had a very strong vibration, particularly at low speeds. So far, I've be able to make it go away by turning off the engine and re-starting it. I thought that this was perhaps due to the dealership filling it initially with regular gas instead of premium, which is specified for the 450h. However, I've now filled it twice with premium top-tier gasoline, and the problem continues to occasionally occur. I've heard of hesitation and vibration problems on the non-hybrid RX350, but didn't think the hybrid 450h (which has a CVT) was affected. Has anyone experienced this or have any ideas about the problem could be, and why it is only intermittent? Thanks.

ggebhardt

Sounds to me that maybe the engine is skipping. I would get it to the dealer to have them run a diagnosis.

Should be smooth.

raytheagle

How many miles on your RX450h? Do you ever perform small moves and not allow for the engine to complete the warm up cycle?

This is a common Gen3 Prius problem when someone swapped driveway spots and didn't let the engine stop on its own. The next time you start it, you would get a knock from condensation sucked into the intake.

ggebhardt

Small moves? My 450h motor seems to warm up very quickly.

raytheagle

But if trying to move the car in EV mode and the engine fires, do you let it complete? This would occur then the car would sit prior to the next start, and this problem would arise. If not condensation could develop causing a small knock on startup. This phenomenon is at least common on the Gen3 Prius with the egr system.

ukrkoz

At TCH forum we have pretty much consensus that knock/shudder at cold start ups is due to low oil pressure in the engine. I experienced this in my TCH quite a few times until engine was overhauled under high oil consumption recall.
Oil simply leaks down into the oil pan resulting in loosened chain tensioner resulting in timing slightly off due to loose chain and chain rattling, till oil pressure builds up and tensioner tightens the chain.
it can be quite a ruckus to be honest.
Moving hybrid vehicle few feet across the parking or driveway creates NO vapors stuck anywhere as, normally, it is done in EV mode only and ICE does not even turn on. Same token, as ICE does not turn on, oil pump does not build pressure into the system. We had several owners that had this rattle after they moved their TCH up/down driveway and let it sit.
Just saying.
Shudder at point speed 45mph is actually normal as that is what cut off speed and transition to ICE is. When a 6 cyl ICE turns on, there is always some shudder, more or less. But nothing excessive.

ukrkoz

I would. That is what I did with my TCH after few cold start shudders and research. Builds up oil pressure in the system. Mof at some point, before they fixed my engine, I would actually turn system on and sit and wait until it turns on only THEN move. If I employed that technique, I never had cold start shudder.

ggebhardt

What are you talking about. I completely ignore the fact that my vehicles are hybrid and just drive it. I do not worry about the engine "completing" anything.

My 450h leaves the garage everyday as an electric and then the motor starts seconds later. Never had any problems and I am in and out of the vehicle all day long. So far both of my 2017 450h models have worked without flaw. I also owned a 2016 450h and never had the problems you are talking about.

The OP needs to take his vehicle to Lexus and see if they can find something in the diagnosis.

pdaeng

definitely not because of regular gas. I use regular gas exclusively for my 16 RX450H, no problem at all.

Nogee

IrishJoe,
I am having similar symptoms with our 2016 with about 41,000 miles. I notice that on initial startup in the morning that the car seems to stumble between combustion and electric mode. It is similar to having an idle that is too low or bad fuel as in a non-hybrid car. There is also an intermittent "clacking" noise during this brief period.
I also experience some light stumbling during normal driving, but this seems to clear up when the car gets to warmer operating mode.

Did you get any resolution on this? I would be interested to hear your ongoing experience with this issue.

thanks

IrishJoe

Nogee,
In my case, I've found that the problem only occurs if I drive over a section of a local four-lane road that was partially built over a former iron mine. There is a strong magnetic force in the area that reportedly affects steel-belted radial tires. If I drive on the same road in the outside lane (which was not built over the iron mine) I don't experience the vibration. I don't experience the problem on any other roads, so I've concluded that my RX 450h is not at fault. Best wishes on resolving your issue.