Quite a weird experience yesterday. I was in the RX450h with my son, everythings fine, its running smooth like a purring cat. I get to the bottom of the hill at a traffic light and stop with my foot on the brake.

Then it just started pulsating, engine comes on, goes off, comes on again, goes off - almost like a pressure washer with an internal leak

It went away after 30s or so and hasnt come back. No engine lights or hybrid system warnings. Any ideas what it was?

 

Not having been in the car at the time, it sounds like it could have been running to replace some depleted energy in the traction batteries. Did you happen to notice the traction battery level?

 

I checked the hybrid battery. First thing I did, it was close to full which was why it was rather wierd.

Also it wasnt running, it was going on and off repeatedly

 

rayaans, I go down (and up) hills every day and haven't experienced any issues with the engine pulsating. I wonder if it has anything to do with the regenerative braking and/or temperature. Have you tried going down the same hill again? Hopefully it was just a fluke. Definitely let us know what happens.

 

Over the years I have heard of this happening on other Toyota hybrids, but it is very rare. I had it happen to me once in the 6 yrs I had my Camry Hybrid, not seen it specifically on the RX, but also heard of it happening on Prius. The system programming seems to get into some kind of funk when coming to a stop apparently resulting in conflicting status flags (ie the engine needs to run, but the engine does not need to run). It goes away as soon as their is another state change (ie driving away from the stop, or some other change in sensor readings that cause the status flags to be updated). There is another rare similar incident where the engine will refuse to shut off after coming to a stop (even on a mild summer day, engine warm and happy, battery charged, no A/C demands, the engine will absolutely not stop running even if parked for many minutes. Again, it clears simply by driving away and might never happen again.

 

Its never come back, driven a good 200 miles since then! Its the first time it happened so was just wondering what it could have been but glad its not back.

Anyway, even if there is an issue, hopefully itll get picked up in my 30k service this month! Thanks for the info guys!

 

Maybe it was the hill assist.
Push your pedal down very hard when on a hill or even flat. Perhaps it was just trying to hold you there. I know the light goes on and the brake vibrates when doing this.

[QUOTEQ UOTE=rayaans;9023913]Quite a weird experience yesterday. I was in the RX450h with my son, everythings fine, its running smooth like a purring cat. I get to the bottom of the hill at a traffic light and stop with my foot on the brake.

Then it just started pulsating, engine comes on, goes off, comes on again, goes off - almost like a pressure washer with an internal leak

It went away after 30s or so and hasnt come back. No engine lights or hybrid system warnings. Any ideas what it was?[/QUOTE]

 

[/QUOTE]

Nah it wasnt the hill assist. Ive used it on many occasions and it doesnt do that.

Also, there was no elevation so it would have caused the engine to start and stop repeatedly. Anyways, the good thing is, it hasnt come back!

 

Does anyone know if pushing on brake and gas petals at the same time will do this? Isn't it true the '10s didn't have the brake override and '12s and newer did? Personally on my '12 I don't think it works properly.

Just wondering.

 

I believe Smart Stop Technology came in with the 2011 RX.

 

Bert is correct. It was part of the settlement for '10 owners.

 

Somewhere in my technosearch I came across a reference that the brain tries to "park" the engine on a particular compression (or lack thereof) index.

If so, it could explain what I perceived to be several attempts at shutting off the engine - much like the old engines that kept on running due to pre ignition run-on.

Seemed somewhat similar to OP's observation.

 

KITLZ- What "settlement" for "10 owners are you referring to?

 

Lexi450, Lexus issued a service campaign as part of the settlement regarding floor mats and sudden acceleration. There's a few threads on the topic but I think this one has the most details.

 

OP, I would venture a guess that this was due to you stopping at the bottom of the hill.

I did a full brake job on our RX last weekend and took it through its paces to get the pads seated properly.
Lots of braking and stopping going downhill. When I parked it to inspect brakes, it kept turning itself on and off.
It seemed a little off to me, but I did put a lot of stress on it. I think it was trying to cool off the hybrid electrical system by doing this, as I did lots of regen and depletion cycles.