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Discussion Starter · #1 ·
Does anyone have a problem similar to mine? I am not sure what is going on, but when I am on a very slight uphill grade or nearly level roads, essentially holding a nearly steady throttle at highway speeds, I will often feel a bump, and sometimes can see a very slight rise in RPM. The rise is about 100 rpm as far as I can tell. I know the MDS is supposed to be seamless when it de-activates, but I can't help think this might be what it is. It seems like either this, or a torque converter thing because it occurs under conditions where I have a very slight increase in torque occurring. It is the opposite of the problem I am about to describe, but what it feels like is with several vehicles I have had when the torque converter actually locks up when in the highest 2 gears, but occurs when needing marginally more torque, not less like this. I have also noticed these prior vehicles increasing rpm's enough that I could see it when the TC un-locked (200-300 rpm). I have tried to see it with the EVIC in diagnostic mode, but since I can't absolutely tell when it is going to happen, it's tough to drive and look at it at the same time, plus the RPM's are always varying up and down by about 50 or more rpm constantly, even in cruise control. I am just worried that it might be a sign of something worse to come in the tranny or ecm or something in the future. It does happen often enough to be a nuisance. How about it? Anybody else have this problem?
 

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albow,
I don't think you really have a problem. I think it is the PCM continuously managing MDS, torque converter lock, and probably other engine functions to give so called optimal operation under the current conditions. Mine works exactly the same. I use to think it was the torque converter unlocking, but since I have installed my MDS "on" indicator light, http://www.300cforums.com/forums/showthread.php?t=4984
I have noticed that the bump occurs when the MDS is going off. I also think that it may also, simultaneously, unlock the torque converter. I just got back from an 800 mile trip and also noticed that the MDS will stay on longer when the cruise control is active and managing throttle application. The MDS stayed on many times going up slight to moderately slight inclines. When my RT was new (200 miles) I had the converter lockup and it would not unlock. Just before it failed I could feel what seemed like lock, unlock, lock, unlock, several times. This bump was very similar to what we feel on the incline as you described. In my opinion the MDS light just helps manage/monitor the MDS operation, and at slower speeds you can coax it to come on when it normally would not be on. Also, for your info. the MDS will only operate with the selector in the "D" position. You may want to experiment over the same route with selector in "4" and see if you still get the bump. Then you would know it was the converter, IMO. Keep us posted on your findings.
 

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Discussion Starter · #3 ·
Thanks. I've got a feeling that's what it is, but I have seen nothing but writings in the magazines saying people are unable to tell when it activates or de-activates because it feels seamless. If so, then why do you and I feel it and others aren't feeling it? Might it be portending a future problem with the system? I think I will be sure and mention it to my dealer at my next visit, just so it will be recorded.
 

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I have felt a bump and in my case I think it is the A/C cycling on and off, try turning your climate control to off and see if the bump goes away.
 
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