natsibley

There seems to be a delay issue on the brakes on our RX300. The pedal feels the same (pushing pressure, etc.) but the car seems to hesitate before the brakes actually start working. What might be the problem here?

Also, my wife said that the last time she parked the car, right after she put it in park, the engine revved up on it's own.

My wife has had this car for many years and we've both driven it a lot with very few problems. Odd that two seemingly unrelated problems like this would show up at the same time. Any chance there could be a connection between these two? (I sure as heck can't see one.) I will respond very quickly to requested for more information.

Lexmex

The second issue is likely related to the IACV and it needs cleaning, https://www.clublexus.com/forums/rx3...-write-up.html

The RPMs can either bounce or they can just stay high in park. Sometimes it will go back to normal, but often there some accumulation in there that just needs to be cleaned.

Not exactly sure on the brake hesitation. Would like to know at what mph she's feeling this hesitation. There's a whole lot of thing that come to mind.

natsibley

Thanks for the tip on the IACV, I will look at doing that very soon.

Waiting for a response from the wife on the brake issue speeds. Could you possibly offer your thoughts on the most likely possibilities here? Based on my conversation with her I would guess she's seeing it mostly at lower speeds (<40mph).

hypervish

What is the condition of the brake pads? It's possible they are worn out.

Lexmex

hypervish mentioned one of them that's the biggest one, worn out pads and that's a pretty even response on the pedal along with low/old fluid as opposed to something like a slide pin losing lubrication or there's also an issue that can happen with the ABS under 5 mph, where there can be a jerk upon braking that a few of the members have had.

natsibley

Just spoke with my wife; she said she noticed the issue at all speeds.

I'd be surprised if it was just the pads, since that would be more of a gradual change as opposed to an all-of-the-sudden-I'm-noticing-a-delay type thing, right? Fluid is definitely at the top of my list of things to check.

salimshah

Talking about brake fluid, it is among the most neglected fluid. It needs to be flushed out every other year.

Then there is the brake 'feel' issue and due to the brake boost, as engine rpm changes the assist changes ... something you can feel when the A/C clutch kicks in and out and the engine rpm is adjusted by the ecu.

Salim

natsibley

Can you elaborate a little more on the brake boost? I'm not familiar. How does it relate to the A/C clutch? What does the A/C clutch do? When you mentioned the A/C I remembered that my wife had mentioned that the vehicle didn't seem to be cooling as well as usual.

natsibley

Status update:

My wife has just informed me that she does not believe there is a problem with the brakes, only with the accelerator. The revving issue is occurring not only while idling, but while driving as well (she likely didn't notice before b/c of the radio and/or baby). She believes this is the "problem" with the brakes, that the car is attempting to accelerate while she is braking. Much scarier than the original situation. The car is stranded at the mall for now. Anybody have any thoughts?

Lexmex

Take a look at the IACV valve. The only other issue offhand is the accelerator cable may be loose/caught and needs to get tightened, https://www.clublexus.com/forums/rx-...se-advise.html

As I also mentioned, somewhere just under the 5 mph mark, when coming to a stop, the vehicle can jerk (happened to me in Mexico and I disconnected the ABS and no more issues) when it appears you've come to a full stop and then it lurches forward.

If the RPMs are flying around, staying high then it's the IACV.

LA4Mead

An obvious item to check: floor mats. Factory driver's mat must be secured with the factory retainer. Aftermarket mats can work their way up and possibly interfere with the accelerator although much more likely to cause trouble accelerating. See if there is something else interfering with the operation of the throttle both under the dash as well as at the throttle assembly, but you likely already checked that. Good luck.

salimshah

If you think there is problem, please take the vehicle to a Lexus dealership immediately and try not to self diagnose/fix on your own. I say this because, I am of the opinion that there are no design flaw with the RX and folks with home-cooked remedy can cause real problems. With the disclaimer out of the way ...

The RPM gauge (which I always thought is useless in auto-trans) can give you more accurate information and cut out the other factors.

When the A/C runs (as controlled by thermostat) the A/C clutch engages and disengages. To compensate for the additional load on the engine, the idle rpm is bumped up. You can see that on the rpm gauge and feel it in the brake-pedal when you have it depressed (stopped at a traffic light).

Salim

Tanjee

Hi, I know this post is old but I need your help. Exactly as your wife has described, it feels like the car is either accelerating on braking hence creating a delayed braking which ultimately feels like the car is not going to stop when braking. It has created small panicks when driving. It is happening both and high and low speeds with the AC on. Did you find the cause of your wife's problem. It feels very scary when you press the brakes seems like car accelerates a it then when you press lower it stops. It's very uncomfortable.

salimshah

Tanjee, Welcome to CL.

Please read and follow my suggestion to natsibley.

There are no known problems in RX that can cause what you are experiencing. When it comes to safety, why would you be polling for opinions by non experts.

Have the dealer check for vacuum leaks. I had a rip in one hose that threw a CEL but I felt lack in braking power.

Salim

Tanjee

Thank you for responding Salimshah, and I truly understand and appreciate your comment. I need to say to you that I have done lots of research only to find that there has been tons of issues with this. As a matter of fact, America made Toyota/Lexus pay BILLIONS of dollars for the cover up of what is call unintentional acceleration in the vehicle. There are also tons of documented accidents regarding the matter. I will call the Lexus dealer I just wanted to know if the original poster of this forum was given a resolution to the problem. USA today wrote an article on the matter in 2014. If you google "lexus accelerating while braking" you will find news articles regarding the matter and if you add the 2001 RX 300 you will find TONS of people who said they had accidents due to similar experiences.

I just wanted to know if his problem was in fact resolved by the dealer b/c I've also seen post where dealer denies the fault yet years later they had to pay billions for the "cover up" for an issue that was said was known by the company.

http://abcnews.go.com/Blotter/toyota...ry?id=22972214

It reads Toyota pays 1.2 BILLION for hiding deadly unintended acceleration.

I heard it might be an issue with a throttle sensor but if Toyota/Lexus has been hiding the issue what value is it to bring it to a dealer who will tell me they have no idea what I'm talking about and that I'm "crazy?"

I want it fixed I don't want it covered up, so I hope the original person replys to tell me if they covered it up with him or in fact resolved the problem.

Salim, I'm thinking you may work for Lexus b/c you said there are no grounds for the findings? Thank you, I do sincerely appreciate your concern.