Last post on Jun 17, 2013 at 12:55 PM
You are in the Lexus RX 400h Maintenance & Repair
What is this discussion about?
Lexus RX 400h, Engine, SUV
#67 of 76 Re: Mr. West--help [wwest]
May 06, 2009 (8:37 pm)
My Lexus is resting this week--however, when I next drive it, I will try to ascertain whether I am sensing a "surge" versus, as you suggest, a "loosening of braking." You may be correct that what I am experiencing is loosening of braking. I would never take my foot off the brake to coast into a parking place so should not smash into anything. I had the car checked again at the Lexus dealer and nothing appeared to be abnormal.
Thank you for replying.
#68 of 76 Re: RX400H surge power on stopping [wwest]
May 17, 2009 (4:40 am)
Here is my pennie's worth!
I have a 2006 400h and I notice when going down a steep hill, especially when the engine is cold, (but perhaps that is when I hit the first steep hill) that as I am gently braking the regen is putting a nice amount of power back in the battery and the meter is well into the blue, then after a few seconds the braking lifts off for a fraction of a second, the car runs away and the charging stops but the friction brakes kick in.
However, I think that is because I subconsciously press the pedal slightly harder and all is well again. Then I release the pedal and press gently and regen kicks in again and drops out after a few seconds and the process continues as described above till I get to the bottom of the hill.
I thought that was normal and happening because the regen wasn't able to provide enough braking but perhaps not....
I am used to it now and it's no problem to me.
Enjoy your car.. I do I have no intention of changing it for another 10 + years!!
#69 of 76 Re: RX400H surge power on stopping [billysbarn1]
May 20, 2009 (6:29 am)
My '01 AWD RX300 does something strange, "washboardy" road feel, when lightly braking going down a slight grade with the roadbed wet. It's as if the ABS is very lightly modulating the brakes. I seem to remember that someone at the dealer told me that it was the EBD, Electronic Brakeforce Distribution, activating.
If your "H" has the same EBD feature then it is likely that regen would have to be disabled when it activates.
#70 of 76 Re: Mr. West--help [nmrk]
Jan 30, 2010 (11:44 am)
My car has not been resting all of this time, my mind is.
It is a surge. I can feel the forward jerk and, so can my sister. She had this problem with her Grand Am.
I have not been in a situation where I had to brake at high speeds. I should check it out just out of curiosity. I have not established a pattern for this behavior and it is totally intermittent.
Lexus no longer responds to my emails. I guess they have enough problems. I now have 20,000 miles on the car and must replace the tires.
Thanks for your help.
#71 of 76 Re: Mr. West--help [nmrk]
Feb 02, 2010 (11:24 am)
I should have mentioned that with the RXh, or any of the FWD hybrids, if even the slightest sign of impending lockup of the wheels is detected then regen braking will be INSTANTLY disabled. Brief slippery spot in the roadbed (plastic crosswalk stripping, railway rail, even a slight bump, can result in a tire losing roadbed traction just long enough to force a sudden transition, NON-SMOOTH, transition.
With light to moderate braking this SUDDEN transition from regen braking, maybe ONLY regen braking, to SOLELY frictional braking might be somewhat JARRING.
You're body's seat-of-the-pants" sensors cannot easily distinguish between a lessening of the braking force and an actual surge forward. If you were in a flight simulator I could give you the same effect as a surge by suddenly tilting the front of the simulator upward.
#72 of 76 Re: Mr. West--help [wwest]
Feb 05, 2010 (5:53 pm)
My Lexus serviceman finally gave me a similar explanation on the "surge." I did turn 20,000 miles.
"You're body's seat-of-the-pants" sensors cannot easily distinguish....."
Are you saying that the problem is my insensitive rear end? And all the while I thought it was the rear end of the Lexus. I won't even ask why the batteries on my Lexus, Prius and Ford truck go dead if not "walked" regularly. I'd hate to think I have other malfunctioning body parts.
#74 of 76 RE: Regenerative braking
Jul 02, 2010 (9:47 am)
To add to this, I also experience a slight surge when the regen braking suddenly shuts off as I'm approaching a stop. It tends to happen if I'm going over bumps in the pavemen, even when the road's dry.
Regarding the question of ABS pre-activation, it's possible, but I have another theory: it could be to maximize the life of the power inverters. Toyota may have programmed the regen braking to shut off if it detects any unexpected variation in the current/frequency of the electricity coming from the regen motors. If a wheel were to slip-and-catch, then presumably the voltage/current that are hitting the inverters are varying wildly. This could put a substantial stress on the electric components in the inverter, and shorten their expected lifespan. Hence, Toyota may have programmed the system to shut off if a significant-enough bump is encountered.
#75 of 76 Engine Humming
Apr 23, 2012 (1:09 pm)
Hello, I have a 2006 RX400h, with 88,000 miles. Garage kept, single driver, routine maintenance since purchase. I have recently had a significant decrease in fuel mileage and now my car has what sounds like, as best I can describe, either an engine 'hum', or a steady engine sound of high idle, like it wants to shift into a higher gear but never does. This occurs at any speed, 15 or 70, it doesn't matter. The sound never changes regardless of the speed. Anyone else having this issue? Or can anyone suggest or advise what this issue might be? Thanks!
#76 of 76 2006 RX400h surged/jumped forward from park on start
Jun 17, 2013 (12:55 pm)
My 2006 has about 250k miles... I'm original owner, did all recommended maintenace. my son leaned into car, turned key (to lower windows), gear shift was in Park; it growled then jumped into the truck in front of it, damaged my car... any idea what the problem could be? anybody else have similar problem?