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Discussion Starter · #1 ·
I while back I remember about another individual talking about how he could feel MDS engaging and disengaging as he travelled on gently rolling roads. No one else seemed to share that experience. I however, think I may be experiencing at least something similar. I live in a rural area where everywhere I go the speed limit is 55mph. I usually use the speed control. I have noticed that if I am cruising at 55mph I seem to feel "something" going on when I come to ever so slight inclines along the highway. It sort of feels like when an engine slightly lugs in a stick car, I feel it in my seat too where it almost feels like I'm driving over a very shallow rumble strip in the road. It is not horrific, but its there. If I increase my cruising speed to 60 I don't notice it. If I decrease my cruising speed to 50 I don't notice it.

Am I (and perhaps the other member - Stephen?) unique or does anyone else ever experience anything like this?
 

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Me, too. The Machinist's are on strike where I live, so once they go back to work, I'm taking mine in. I'm also experiencing some hesitation on light to moderate accelerations from a stop.

I hope this can be corrected. Otherwise I love the car.
 

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Discussion Starter · #4 ·
Yes - it's weird isn't it. It is just at 55mph (maybe plus/minus 1 mph) and seems to come and go with the rolling terain. I too have "worked around it" at least temporarily, by not going 55, but that's not really a solution. Please continue to update this thread if anyone else has experienced this or has any feedback from dealer as far as causes and cures. Thanks...
 

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Yeah, It mine too...but I haven tpaid attention to the speed I am travelling at... I just figured it was the MDS doing its thing.... give it gas, and it goes away, a littl ebreak and it goes away........

Matter of fact I am not sure mine ONLY happens at 55...... I will watch for it now....
 

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As soon as my car arrives I plan on doing some testing on the MDS system. The solenoids that deactivate the cylinders are powered by a 12V signal. When the circuit is powered, the solenoid energizes and the cylinder deactivates. I plan on putting a test LED light on the circuit to monitor the activation/deactivation of the cylinders. With this visual cue, it should be easier to establish the parameters that the system is engaging and disengaging under.

My only real goal of the exercise is to determine if there is a set speed or RPM that the system will not engage under. e.g. If I'm on a road trip and MDS will stay enabled at 75MPH, but not at 80, then I may set my cruise at 75 and not worry about going any faster.
 

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If you really wanted to, you could just disconnect the two wire lead to each of the 4 solenoids and that would prevent it from engaging. I'm sure it would probably toss you a couple of DTC's in the process though.:(

If the system only activates at cruising speeds and can kick back in within a few turns of the cam, why would you need to disable it?:confused:
 

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kampsvilleboy said:
, I feel it in my seat too where it almost feels like I'm driving over a very shallow rumble strip in the road. It is not horrific, but its there.

I feel the same thing, but I feel mine in the gas pedal. I'm taking it in to get it looked at on Friday. I didn't think it was the MDS but then again I don't know what it is.
 

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Discussion Starter · #11 ·
MAF said:
I feel the same thing, but I feel mine in the gas pedal. I'm taking it in to get it looked at on Friday. I didn't think it was the MDS but then again I don't know what it is.
Please... let us know what the dealer says...
 

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I notice it at cruise speed especially with the A/C on (greater load on the engine). But, even with it off, I feel a slight "hiccup" as it switches mode. I can also is the tack guage jump up a couple 100 RPMs, then it drops a couple and finally goes back to where it started.

Not terrible... but noticable to me since I drive it every day. My wife thinks I am crazy! :D
 

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Discussion Starter · #13 ·
Hey MAF, I'm glad this went back to the top... did you take it into the dealer? Did he have any comment/fix for the intermittent vibration near 55mph? Inquiring minds want to know...
 

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I never noticed this 55 vibration until after I had my oil changed. Just like everyone else says it happens at exactly 55 mph. Do you guys think it is just coincidental that I noticed it after changing the oil? Is there a common denominator here?

Has anyone had this checked at the dealer yet?
 

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Discussion Starter · #16 ·
I'm beginning to think C-Man may be right. The vibration feels like a standard trans. car that is being lugged slightly. I notice that frequently I feel it at 55-57,58mph (it seems to move around a bit) when I am going up a "ever-so-slight" incline in the road and it ends by the feeling of a slight shift and a small rise in RPM. It may well be the torque-converter clutch. If so, is this something that a programming change could fix or are we talking about a characteristic inherent to the clutch/torque converter itself? Could it be a defective mount or isolator?

Has anyone yet had the dealer look at it?
 

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I don't think it is the torque converter locking up. At a steady 55 mph the vibration remains constant. If it were the lock-up, it would emulate your tranny shifting to a higher gear.
 

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Just my $0.02, first thought I had is elevation, but if Kampsville is in IL, 440 ft isn't much elevation. Second thought is if there's a weak mount, you might notice a shudder if you shift between d-r and back .
 

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I guess MAF fell off of the earth! No answer from him/her. I still have the 55MPH thing, but it is a non-issue for me. I just don't go exactly 55MPH! Everything else on my "C" is great, so why bother with such a small thing? My $.02

BTW, isn't it great that this is the biggest thing that most of us can &*%[email protected] about?
 

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mdrevs said:
Me, too. The Machinist's are on strike where I live, so once they go back to work, I'm taking mine in. I'm also experiencing some hesitation on light to moderate accelerations from a stop.

I hope this can be corrected. Otherwise I love the car.

I have a 2006 300C. After about the first 1000 miles, I noticed some hesitation when accelerating from a stop. The car seemed to go through some noticable shift/surges/declines. This was most noticable when the engine was ice cold, and on initial acceleration out of the driveway. Anyone else experience this?
 
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