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Discussion Starter #1
I have noticed that on my 08 R/T, MDS kicks in quite hard. It's a lot lighter of a transition in the city, or at low speeds in general. But on the highway, there are times when you can REALLY feel it come on and off. It has like a lurch/jerk effect, more so when it's going up a slight incline.

I don't recall it being that harsh of a transition in my Daytona or the 07 R/T I had, so is there anything I should be looking at? I do know that my front shocks need replacing as they are soft as Jell-O, but I'm not sure if that would be sufficient enough to make the car jerk when switching MDS on/off.
 

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The car doesn't know you're on an incline or what the road up ahead looks like so if you land in the range of RPM and gear where MDS is available, the car will engage MDS, which leads to instantly more strain on the powertrain and likely leading to the jerkiness you feel when it re-engages 8 cylinders. Does it feel similar to hunting for gears? If so, then reading the road yourself and engaging auto-stick to hold a gear and disable MDS may be best.
 

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MDS does recognize load changes and that will engage and disengage MDS. MDS transition should feel seamless. If it does not something wrong is occurring. Are you running a tuner like Diablo? How many miles are on the car?
 

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I would service your suspension first, since it already needs it and could be contributing to what your describing. If new shocks do not change anything then I would investigate possible MDS issue. The MDS is an emissions related component so it monitored pretty strictly by the pcm. Im not saying that nothing is wrong but i think a MIL light. Make sure you oil is at the correct level as well.
 

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Discussion Starter #6
MDS does recognize load changes and that will engage and disengage MDS. MDS transition should feel seamless. If it does not something wrong is occurring. Are you running a tuner like Diablo? How many miles are on the car?
No tuner, 81,000 miles as of today. Car just received an oil change 3 weeks ago, 5W20 Mobil1. No CEL, no anything, really. Just has its moments where it'll go in and out of MDS with a noticeable jerk...
 

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Discussion Starter #7
Quick update: While I have not done my suspension yet, but the issue seems to have gotten a little worse. There are times where I feel like the car just isn't sure if it wants to disable or enable MDS, even if my gas pedal pressure hasn't changed. I then have to put the car into AutoStick or it'll jerk itself in and out of MDS a few times.

Idk if it's related, but if I do a WOT run and then settle myself down, it doesn't seem to happen again for a long time. In any case, when it does happen, you definitely feel it. No CEL, fluids all normal, no pending codes, nada. I'm stumped...
 

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Discussion Starter #8
Reviving this because the issue is starting to get under my skin.

Does the EGR valve cause issues with the MDS? My car is 7 years old but only has 83,000 miles. It has felt sluggish and lazy and MPGs have dropped recently. Could they cause this issue?

Also, could spark plugs be a culprit too? I installed new Champion copper plugs, but stupid me, I didn't check the gap. So my worry now is they weren't gapped properly or something.

Would the MDS reset actually be useful? I've heard conflicting view on it.
 

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Discussion Starter #11

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The same issue happened to my 2009 R/T 9 months ago at 90K while the ticking sound started increasing. 2 months ago check engine light started flashing & engine started shaking.
The code pointed to a misfire in cylinder 3. Changed the spark plugs, fuel injector and coil but no luck :(

the car is at the dealer now and it looks like the problem is bad lifters and camshaft!

I hope this won't happen to you and if there is anyway to fix the problem do so before u get stuck.

Btw have you thought about turning MDS off with diablotuner? Not sure if that would help though.
 

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Discussion Starter #14
The same issue happened to my 2009 R/T 9 months ago at 90K while the ticking sound started increasing. 2 months ago check engine light started flashing & engine started shaking.
The code pointed to a misfire in cylinder 3. Changed the spark plugs, fuel injector and coil but no luck :(

the car is at the dealer now and it looks like the problem is bad lifters and camshaft!

I hope this won't happen to you and if there is anyway to fix the problem do so before u get stuck.

Btw have you thought about turning MDS off with diablotuner? Not sure if that would help though.
I hope it's not that. The car runs great right now, so I'm not sure a misfire is the issue. It may be that I used the "high mileage" Mobil1 5W20. What I do now is just use AutoStick to avoid MDS. It only adds about 1-2MPG anyway.
 
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