| Philth |
Have a Sport/Ent MDX with about 7k miles on it now. My wife has been complaining about the MDX having a throttle hesitation after going over a speedbump, followed with a grinding that she can actually FEEL over the pedal. For the longest time, I'm thinking, "It's drive by wire, how can it possibly grind?" I kinda put it off but ended up taking it to the dealer for inspection. Of course, they couldn't find anything and I didn't really expect them too, seeing how intermittent the problem is.
Well today it happened to her again, and this time she said, "What the little yellow triangle with an exclamation point inside of it?" I told her it's the warning light for the VSA if the wheels slip. She said, "That was flashing too while the hesitation started."
Has anybody heard of or experienced this problem? To me, it sounds like one of the wheel speed sensors are going or something....
I want to take it to the dealer but they are going to think I'm high cause it only does it every once in a blue moon. |
|
|
| highcountrymdx |
Because the anti skid system (and VSA) uses a very fast processor, the system is able to detect even the slightest variation in wheel speeds and react virtually instantaneously. If your wife happened to have her foot on the brake as she encountered the speed bump, as you might expect, the anti skid would be activated, albeit at a threshold level.
What she's experiencing is, in fact, the normal pulsing of the anti skid system. It is much more sensitive than previous versions. Previous anti skid systems would work only during extreme braking. Not so on this car.
I am constantly amazed how accurate and fine tuned the entire system turns out to be. |
|
|
| Mia's Dad |
| The same thing happened to my wife a good while ago. She said that she thought she might have had her foot on the gas a bit while going over the speed bump. That would cause the wheels to spin a bit if the are not making good contact with the bump itself or the pavement. |
|
|
| rerodgers |
| happens all the time to me in my '04 going over speed bumps are larger pot holes. With my foot on the brake the ABS kicks in and pulses the brakes. It was fairly common ont he first gen and I would have thought that they would have made some adjustments on the second gen. |
|
|
| gmc74 |
I am not sure what the issue is, haven't felt it myself, but if she hits the gas while her tires are still on the bump, they are more likely to slip. Most speed bumps are painted, and the paint is very slick, that could be the issue.
No idea really, but I will see if it happens to me |
|
|
| Mike_TX |
Almost a tiny bit off-topic, but I'm surprised more people haven't noticed speed bumps upset your car less if you go over them a little faster. Not 30mph or anything, but if you creep over them, your suspension saws back and forth and the car heaves from side to side. But go over them at 10mph or so, they smooth out pretty nicely.
(Have I ever mentioned how much I HATE speed bumps? ;) )
.
. |
|
|
| pdempsey |
I've had it happen. I hear a little grinding. I just figure it's the computer trying to do something fancy and the speed bump causes some wheel hop.
With my 2003X, there were lots of posts about some rear end grinding or something. I heard that a few times too.
I think these things use clutches, and they probably make a little noise when the get in a strange situation.
I don't lose sleep over it. |
|
|
| Activator |
No question in my mind that it is the ABS kicking in. If you are braking while going over the speed bump, the tires catch a little momentary "air" which the ABS sensor thinks is wheel slippage, so it engages the ABS - thus the "grinding" sound, which is the exact noise ABS makes when engaged! Problem solved!
You don't experince this behaviour when you go 10-15 MPH over the bumps as the ABS dosn't kick in because you're NOT braking!
This is a problem with ABS and motorcycles. Because the bike is so light, small undulations in the pavement can cause the wheels to get "air" and trick the ABS if you are on the brakes at the same time. This can sometimes lengthen the stopping distance. |
|
|
| Hommerun |
Has happened to me a few times..most recently tonight as I was leaving Eisenhower Med Center...took a wrong turn and ended up at Betty Ford Center...big speed bump. As I eased over, I also eased onto the gas a bit...that's when I heard the grinding...no lights lit up however. So I came here to the forums...did a search and bam...here's the issue...in black and white! I was thinking of taking the X to the dealer but based on what I've read here, seems like its just doing its thing.
I had n 05 RL...and after 2500 miles the rear differential failed...had to have the whole system replaced...took almost 3 weeks...so I was a little concerned that the SHAWD system in the X might be coming apart! |
|
|
| hammer604 |
| I have had that exact same thing happen too. It was on a speed bump, and once the warning light came on. |
|
|
| mahen |
I experienced the same thing last night for the first time in my X. I was driving at 15 to 20 MPH over a speed bump when yellow triangle light flashed with a little vibration on the brakes.
When I approached the next bump, I did the same thing without applying the brakes. Guess what... no vibration... no warning light.
I think X is doing what it is supposed to do with its VSA. |
|
|
| eujinc |
| I was able to recreate this vsa flashing rather consistently in Comfort mode with low load over speed bumps. No issue in Sport or if there are people in the back in either modes. Eitherway, from what you guys are saying, this seems to be working by design. |
|
|
| Fabvsix |
When in sport mode going over a speed bump at its INTENDED speed (that it what they are for, not to haul a$$ over them-HELLO PEOPLE!!!!!!) you will encounter very LITTLE squat, lean, nose dive as opposed to comfort mode......:1: :1: :1:
Sport rules......:cool: |
|
|
| arpz |
| its definately abs/vsa working. u'll hear that grinding noise a lot when its slippery out. just to test it out i braked hard on a icey road and the car kept fixing itself trying to stay straight on the road. so i think thers nuthing to worry about ;) |
|
|
| oracion |
quote:
Originally posted by mahen
I experienced the same thing last night for the first time in my X. I was driving at 15 to 20 MPH over a speed bump when yellow triangle light flashed with a little vibration on the brakes.
When I approached the next bump, I did the same thing without applying the brakes. Guess what... no vibration... no warning light.
I think X is doing what it is supposed to do with its VSA.
Very interesting. That's exactly what happened to me a few days ago and I did thought about bring my X to the dealer. However the next time I went over the same speedbump, I just slow down more and got my foot off the gas pedal. That time I didn't see the yellow triangle light and no grinding noise or vibration on the brake. I guess it's just functioning as designed. |
|
|
| wiscogirl |
| thanks for the info. |
|
|
| cybergeek99 |
My '07 MDX is still in the shop, but the Service Manager's explanation was that the VSC was acting normally. I completely disagree and have no confidence in that assessment. If the VSC stalls the car's forward progress and the module grinds, then the sensor mechanisms are too sensitive and there should be an adjustment or re-programming of the code that triggers the VSC to kill the throttle. My wife can get our MDX to do it consistently over speed bumps and with the service tech in the car. It's a flaw; plain and simple.
Acura should have a concern about fixing the problem instead of trying to explain it away. My car has 300 miles on it and I just don't accept their explanation. |
|
|
| highcountrymdx |
quote:
Originally posted by wiscogirl
My dealer considered it a very serious problem.
Nicole
At a shop rate of about $100/hr a lot of dealers would consider anything a serious problem.
cybergeek99-
There's a lot of folks on this forum that do not consider the cycling of the antiskid system when traveling over a speed bump as a "serious" problem. Indeed, your characterization of a 'grinding' noise may, in fact, be no more than the antiskid valves rapidly recycling, just exactly as they're suppose to do.
Try this:
Find a speed bump that you can repeat the symptoms you describe. Traverse the speed bump several times at a speed that will create the 'grinding' noise. Now go back over the same speed bump, only this time do not apply the brakes. Next, try the speed bump at a crawl. See if these two actions changes things. |
|
|
| cybergeek99 |
It doesn't seem to matter whether the brakes are applied or not. Simply coasting over the speed bump does not trigger anything, as would be expected. The system was designed to prevent someone from losing control by hitting the gas once traction was lost. If the VSC is detecting that traction is lost while going over a speed bump, after the front wheels have gone over and I slightly accelerate to continue momentum over the bump, then I would consider it to be out of adjustment or failing to engage properly.
The difference in height between the front wheels and the rear when it's up on the bump could be no more than 4-6 inches depending on the specs of the speed bump. Why would this seemingly small difference in the declination angle trigger the VSC? I am concerned that when it needs to actually do the job, it won't. The dealership explanation that the VSC is operating normally is unacceptable. |
|
|
| highcountrymdx |
cybergeek99-
You keep referring to the suspect subsystem as the VSC. To be as gentle as I can, your vehicle does not have the VSC system that the earlier year MDX's had. The VSC system was replaced in 2007 with the SH-AWD, or Super Handling - All Wheel Drive. This feature set did include "Direct Yaw Control" that functioned along the same lines as VSC. It might be helpful if your dealer talked specifically about the systems in your vehicle.
BTW - The VSC will not be activated unless there is a difference between the steering wheel angle, and the yaw rate sensors. Direct Yaw Control has a similar function. Therefore, I'm wondering if we should be looking somewhere else. There might be two other systems at work here, namely the VTM-4, and the antiskid system.
Additionally, one other thing might be going on here. When you go over the bump, is your foot on the accelerator? If it is, maybe part of the dynamics of the situation might involve movement of your foot on the accelerator, as the car bounces up and down. You see this when traveling off road. It's a very jerky ride, characterized by sudden accelerations and decelerations, when traversing especially bumpy terrain.
I've ridden with some folks who, because of seat position, are not able to keep the heel of their foot on the floor, and the ball of their foot on the accelerator. Instead, they rest their entire foot on the accelerator. In this case movement of the vehicle, if abrupt enough, can be transmitted to the accelerator.
Again, try various combinations of speeds, and foot positions. Brakes on, off, foot on accelerator, and foot flat on the floor. |
|
|
| craniotes |
FWIW, on any given weekend there are seven speed bumps of varying design that I must drive over if I'm to maintain my standard routine (yes, I've counted them). Regardless of speed, suspension settings, or vehicle load, I've yet to trigger the ABS or VSC when traversing these benighted barriers to my forward progress.
With respect to those who are experiencing this issue, it seems to me that a lower triggering threshold for either of these systems would only make the car that much safer. I say this simply to allay concerns that your respective X's are somehow unsafe to be driven on public roads. That said, given the nature of the systems in question, you should definitely have this issue settled to your satisfaction by the dealer. Please keep us updated with your progress.
Regards,
Adam |
|
|
| bigpecs1 |
| has anybody experienced this "grinding" feel/noise on even terrain on very slow speeds, like 10-20mph? |
|
|
| JL_SS |
quote:
Originally posted by cybergeek99
My '07 MDX is still in the shop, but the Service Manager's explanation was that the VSC was acting normally. I completely disagree and have no confidence in that assessment. If the VSC stalls the car's forward progress and the module grinds, then the sensor mechanisms are too sensitive and there should be an adjustment or re-programming of the code that triggers the VSC to kill the throttle. My wife can get our MDX to do it consistently over speed bumps and with the service tech in the car. It's a flaw; plain and simple.
Acura should have a concern about fixing the problem instead of trying to explain it away. My car has 300 miles on it and I just don't accept their explanation.
Has anyone taken your wife out in another new MDX to try to duplicate the issue? If it doesn't happen in the other MDX, then yours has a problem and the service manager is wrong. Seems to me that that would be the starting point and would negate/validate the service managers "explanation". |
|
|
| cybergeek99 |
Yes, the dealership service manager was able to get two of the other MDX's with VSC to repeat the same grinding noise as the VSC took control of the accelerator and apparently activated the anti-lock braking system. I say apparently because I have activated the anti-lock braking system on numerous vehicles and the one constant was the grinding noise and pulsating sensation of the the brake pedal, which the MDX does.
So, I suppose if all of the MDXs can repeat the same results then it must not be a flaw, right???
Wrong. I still say that the MDX has a problem with the Vehicle Stability Control. I just hope that it does not cause anyone to break down at the worst possible moment. It's an inconvenience at this point, not a safety issue in my opinion. |
|
|
| Rokoji |
Cybergeek,
I have a very similar problem. Although I have never experienced the ABS kicking in over the speed bumps, the VSA has engaged 4 times in 6 months during acceleration over speed bumps at low speeds. Dealer has said this was normal and I argued with them that the system was too sensitive. I truly hope that the wheels are slipping and the VSA is doing its job.
You noted earlier that this might be a safety issue if the VSA does not engage when it is supposed to.
I would argue that given the sensitivity of the system, it is a more real possibility that it engages at the wrong time, you lose power and are unable to avoid a car. |
|
|
|
