Mds issue?

[crazykid1994]

I've noticed lately my truck won't engage mds above 55mph. And above 50 seems to be having an issue holding mds. Only mod done to the truck was a carven muffler swap and that seems to be about the same time I noticed the issue. Anyone have any ideas or similar issue? I've always listened to the exhaust tone to notice mds kicking in and off.
Edit: truck is a 2017 had 6000 miles dealer did oil change at 5000


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[Ramnewbie]

What oil did dealer put in? The dealer put 0/20 in my wife's van stating that they were putting 0/20 in everything now. I didn't think it was running right but thought it was me because I hardly ever drive it, however she brought the subject up saying it felt like she really had to stand on it to get on freeway. I changed the oil back out with 5/20 and now all right with the world. I know some will say that there shouldn't be any difference but for some reason her penstar don't like 0/20. When I had dealer change oil in my ram I took in my own oil and filter, that way I know what's in it.

 

[crazykid1994]

Receipt said 5w20. I made sure to double check. It was running fine after the oil change. Muffler has only been on for about 500 of those 1000 miles


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[69GWC]

Mine has not had any issues after the Carven install, MSD kicks in just fine at most any normal speed.

 

[Ramnewbie]

The only other issue would be less back pressure from you're muffler, someone more knowledgeable than me will have to address that issue. I haven't or don't plan on doing any exhaust work on mine. Theoretically the MDS runs off of oil pressure but who knows with all these computer controls.

 

[crazykid1994]

I did get mds to engage at 60 on my way home. I slowed down from 65 to 60 and it engaged immediately, but not from accelerating up. Might pull the battery leads this weekend and let it get a reset.


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[boomer632]

From my experience with MDS, it will not engage if the truck is pulling under acceleration. Mine turns off when it feels the engine lugging at any point. With that said, while on, I can slighly accelerate and maintainin a constant light throttle or deceleration but as soon as it senses a load it turns off.

 

[crazykid1994]

From my experience with MDS, it will not engage if the truck is pulling under acceleration. Mine turns off when it feels the engine lugging at any point. With that said, while on, I can slighly accelerate and maintainin a constant light throttle or deceleration but as soon as it senses a load it turns off.

After accelerating it would turn on almost immediately before. Now it won't turn on. Only after I slow down from a higher speed. Hopefully a reset will help


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[Hemi395]

Did the dealer do a flash when they did the oil change? If they did, it could have different parameters for MDS...

 

[ncgrl1]

You will lose low end torque when you change to a lower restriction muffler or add a cai. What you are doing is moving the powerband to a higher rpm. You will increase horsepower in the higher ranges, but will lose some on the bottom end. That would explain why it's not working the same now...

 

[crazykid1994]

If they did I'm not aware of any flash. Nothing on the receipt for any flashes and I was not told they did any and that would be reasonable to understand about the power band difference if cruising at 65 to 70 wasn't 1800 Rpms in 8th gear. I have 3.92 rear end


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[69GWC]

I dont see that, we have the same muffler and close to the same truck and mine comes on all the time.
It also has been coming on pulling my 6x12 trailer (empty) and I wish it would not..lol

 

[Hemi_1340R]

I have a 16 with 3.92 rear end and have a magnaflow muffler it will only kick on for a second or two even at 50 but in town it will kick on all the time I hate it and turn it off most of the time doesn't get me any better mpg on the highway cause it doesn't stay on long enough


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[Hemi_1340R]

You will lose low end torque when you change to a lower restriction muffler or add a cai. What you are doing is moving the powerband to a higher rpm. You will increase horsepower in the higher ranges, but will lose some on the bottom end. That would explain why it's not working the same now...

I was wondering about that because the magnaflow is basically a straight through design and I had a flowmaster 50 HD on my 05 hemi and it never felt sluggish down low


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[huntergreen]

I dont see that, we have the same muffler and close to the same truck and mine comes on all the time.
It also has been coming on pulling my 6x12 trailer (empty) and I wish it would not..lol

Are you sure the MDS is coming on? Or are you just going by the eco light ?

 

[Ramnewbie]

Are you sure the MDS is coming on? Or are you just going by the eco light ?

I think I'm about to learn something here, I thought if the eco light was on that it meant that MDS was activated. Enlighten me, I'm willing to learn.

 

[ColdCase]

Eco mode (when eco is lit) and MDS are two independent things. You can be running eco with MDS engaged or not.

MDS will disengage with any kind of power need. If there was something done to change the power curve enough, or a dragging brake, or using fuel with more ethanol in it, or larger tires that requires a bit more throttle than before, MDS will not engage as much.

There could also be something mechanical awry. Something change in oil pressure.... could be a bear to figure out.

 

[Ratket]

If the truck is under any sort of load mds will not activate. I don't know how u wouldn't know it is t on. When it drops 4 cylinders the feel of the truck should change. It should easily activate at hwy speeds in stock form.. Now - Lvl kit/lift kit/ bigger tires- These three things will make it harder for mds to activate.

 

[Ramnewbie]

Eco mode (when eco is lit) and MDS are two independent things. You can be running eco with MDS engaged or not.

MDS will disengage with any kind of power need. If there was something done to change the power curve enough, or a dragging brake, or using fuel with more ethanol in it, or larger tires that requires a bit more throttle than before, MDS will not engage as much.

There could also be something mechanical awry. Something change in oil pressure.... could be a bear to figure out.

I love this site, learn something new every day. Thanks for the info guys, keep up the good work.

 

[Ramnewbie]

So what you're saying is the Eco light being on only means that it has the ability to shut down half the motor if it sees fit. Here I thought my mds was smoothest thing ever, out of all the times that my Eco light is on there's only a few times that you actually notice it.