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Discussion Starter #1
I searched but cant seem to find any threads related to our issue. Our 2014 MDX has been pulsing a little when accelerating under light to medium loads. It's a CPO so still under warranty and we brought it in and they supposedly did a software update on the AT but it didn't change. IIRC a while back when it had the B123 service I took it in for the drain and fill and I did the rest. It's really not too bad and my wife who drives it mostly doesn't notice it but I do since I drive a BMW and a Tacoma that accelerate normal. To be honest I cant really tell if its the tranny or engine like fueling or something? When its doing it you can feel it and actually see the revs fluctuate some as the revs are climbing (not related to a shift). So as I said it seems like it could be a fueling issue or slight tranny slipping but at full throttle it seems to be fine? Wierd? Next time we have to take it in I'll bring it up again just wondering if anyone here has experienced the same thing.
 

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I suspect it's in VCM mode while it does that. I have the same exact behavior with my MDX, hesitation, vibration, rattle, wiered RPM fluctuation, etc. When it does that your rpm is probably around 1200rpm. After multiple visits to the dealership, I ended up installing VCM muzzler, which seem to help.

Based on my experience, I think the mdx struggles to switch from VCM mode probably due to fuel supply issue. Its behavior sometimes mimics like cylinder misfire, I guess.
 

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+1 on the VCM. Sounds just like mine. I have a few mile drive at 30 mph every time I leave my house, and it runs like poop as soon as it warms up and enables the VCM. I lock it it 3rd gear, which keeps it about 2000 rpm, and that smooths it out, since it's not lugging at 1500 rpm on 3 cylinders.
 

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Hmm interesting? We've had the MDX for almost 3 years and I've only noticed it the last 6 months or so. Is there a software fix or something the dealer can do about it?
 

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Can you post how many miles on your MDX?
I bought it used at 50k now I am just over 60k miles. I am wondering if dirty engine is causing the issue since not everyone is experiencing it.
 

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Sounds like the transmission fluid problem to me. It degrades prematurely, a flush and refill fixed the problem for me.
 

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What Texus said... it’s likely the tranny fluid degrading. There’s a TSB with 80k warranty for changing trans fluid and updating software. Ours only did it in hot weather (80+). Fluid change fixed it but I expect it’ll be back in time/miles.
 

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Discussion Starter #8
Can you post how many miles on your MDX?
I bought it used at 50k now I am just over 60k miles. I am wondering if dirty engine is causing the issue since not everyone is experiencing it.
46k mi. Okay so this morning started it up cold ran perfect on the way to church 2 mi away. After church on the way home it was doing it. Not hot weather 68F and the car not quite up to temp but close. Does VCM not work when cold? I think it's time to bring it in again. Still under CPO warranty. Thanks I'll report back after. May be a few weeks though.
 

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What Texus said... it’s likely the tranny fluid degrading. There’s a TSB with 80k warranty for changing trans fluid and updating software. Ours only did it in hot weather (80+). Fluid change fixed it but I expect it’ll be back in time/miles.
Do you or anyone have the TSB pdf handy? I'll search around. Thanks
 

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VCM kicks in after reaching normal operating temp. If tranny fluid is the issue, why is my MDX which had the 3 time fill/flush TSB applied in the last year still having the issue?
 

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It's possible your tranny fluid could have degraded again badly enough in a year I guess? But really I think the way to distinguish between the ATF problem vs the VCM is just the tachometer? I haven't heard of the VCM issue causing the tach needle to bounce a bit, but the ATF issue it does.
 

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Not saying it is. I'm asking you to distinguish by symptoms. Just don't totally discount the ATF aspect here, as I'm not sure many owners know what to look for in these vibration type issues.
 

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My 14 was doing that same thing when I bought it CPO. Dealer did the tranny software update and flush. That got rid of it but now 15k miles later it's doing the torque converter judder again. I think the VCM is prematurely degrading the tranny fluid because it kicks in at the oddest intervals and causes the whole car to rattle. I can't believe that's good for the tranny.
 

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If it is a tranny fluid issue, how come the issue diasppears when I install vcm muzzler?
There could readily be something that'd be 'felt' related to something like the VCM kicking in, which affects the torque to the tranny, which could cause the tranny to shift or react in some way, which could even cause a bit of feedback loop causing the VCM to disengage, which could then..., which could then potentially be what's being felt by the few posters here. In other words, what some may be faulting the VCM for may really be related to something with the trans.

In this discussion it'd be interesting to know the drive mode people are using and of course, the type of trans, 6sp or 9sp, is relevant. On my 2014 I almost never notice the VCM at all and when I do it's subtle and really only noticeable, very subtly, at freeway speeds when the power demands are changing due to an incline or the like, but I leave mine always in Sport mode. I can see that the drive modes may have an effect in this area since it affects the shift points, engine responsiveness, and the like.
 

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@mdxstang, are you saying your MDX does not switch to VCM at low speeds like less than 40mph? If that is true then there is definitely something wrong/different with my MDX.

With VMM muzzler (lowest resistor, yellow), my MDX drives exactly like how your MDX drives.

Could this be a coolant temperature sensor possibly different? I can't think of any other reason, somehow slightly lowering the temp(using the resistor) the problem disappears.

Mine is 2014, sh-awd tech.
Below was done by dealer within the last 10kmiles,
3x flush/fill
Torque converter replacement
Software update
Front engine mount replacement

None of the above solved the problem
 

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are you saying your MDX does not switch to VCM at low speeds like less than 40mph?
I've never noticed it switching at those speeds and I'm one pretty in tune with what the vehicle's doing. Do you drive in Sport or do you use comfort or normal? The characteristics of the vehicle change with each of these modes and a lot of it's determined by torque load, which is also how the VCM decides whether to switch on or off - as well as the trans shifting up or down.

I'm just trying to figure out why yours and another poster's seems to behave the way you describe when mine doesn't. When I first got the vehicle I really was expecting the VCM switchover to be more noticeable and found that I have to really pay attention to notice it at all.
 

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Thanks for the thread. I’ve noticed Similar pulsating, the wife pointed it out (her car) but I don’t have as detailed SITREP. But - 2015 MDA, pulsating happens with warm engine at light engine load, 46k miles, no tranny flush, bought used at 30k.
I’ll monitor this thread, maybe try tranny flush and VCM(?). But gotta fix it — MDX is great ride — hate to have this nagging issue (that I figure likely won’t go away).
 
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