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Hi. I searched the forums but didn't come up with a definitive answer. If someone has a thread they can point me too, I'd appreciate it.

I'm replacing the 5.7 in my 2006. I ordered the engine from ProEngines this morning. I'm trying to decide if I should replace all 4 MDS solenoids or just reuse the ones from the old engine and if I have issues, disable the system. I'm planning on a TrailDash2 already and the $250 for 4 MDS solenoids will get me half way to the TrailDash2. I'm planning on using the TrailDash2 to retune to low octane fuel. This is my first vehicle with MDS. I also got this Jeep with a bad engine so I haven't verified if there are issues with the system or if I like it or not. From what I have gathered, the MPG gains are small but the annoyance and issues can be large.

Any thoughts or advice?
 

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A lot depends on your driving style. MDS is great if you have a light and steady foot, or use cruse control a lot. I find that on my morning drive to work I make some good MPG gains, but then burn it all up (and then some) on the evening drive home. The 5.7 can be a thirsty beast.
 

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The solenoids don't really ever go bad. If i remember right, if they are to fail then they fail OPEN rather than closed, so they won't affect the lifters at all.
You should be fine to just transfer the old ones over. If the new engine didn't come with them, and you don't want to transfer, you'll need to get the solenoid plugs to block off the holes. And definitely disable MDS with the tuner. Like THESE plugs.

If you swap the solenoids over and later decide to disable them with a tuner, you'll be good. HOWEVER, if you don't put any solenoids in (new or old) and just install plugs, you might have to run the non-MDS lifters. I'm not 100% sure on this as I was seeing mixed answers around the other HEMI sites. Usually the MDS delete kits come with these plugs AND lifters. I'd do some further research if you are considering this route.
 

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You can disable the MDS temporally if you want . Press the "Tow/Haul" button and MDS is disabled. It also puts the trans in one lower gear. Use as a trouble shooting aid?
 

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Discussion Starter #5
The solenoids don't really ever go bad. If i remember right, if they are to fail then they fail OPEN rather than closed, so they won't affect the lifters at all.
You should be fine to just transfer the old ones over. If the new engine didn't come with them, and you don't want to transfer, you'll need to get the solenoid plugs to block off the holes. And definitely disable MDS with the tuner. Like THESE plugs.

If you swap the solenoids over and later decide to disable them with a tuner, you'll be good. HOWEVER, if you don't put any solenoids in (new or old) and just install plugs, you might have to run the non-MDS lifters. I'm not 100% sure on this as I was seeing mixed answers around the other HEMI sites. Usually the MDS delete kits come with these plugs AND lifters. I'd do some further research if you are considering this route.


Thanks for the input. I'm planning on swapping the solenoids over and if they work, great! But if they don't I'll go the disable route.


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Discussion Starter #6
A lot depends on your driving style. MDS is great if you have a light and steady foot, or use cruse control a lot. I find that on my morning drive to work I make some good MPG gains, but then burn it all up (and then some) on the evening drive home. The 5.7 can be a thirsty beast.


I'll swap the old ones over and hope for the best. Thanks!


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Where’s Mongo? Yes, the solenoids can go bad. I just replaced one of mine. I was getting misfire codes for cylinder 6. Turning off MDS via tow/haul mode solved the problem temporarily. Replaced the MDS solenoid...no misfires. Personally, I’d ditch the MDS unless you do a lot of commuting. The 09-10 system works much better, but my 06 sucks it down no matter what I do. By the way, I also have the HemiPro. Going strong since 2016 when I lost the factory engine to a dropped valve seat.
 

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Where’s Mongo?
@Mongo has not been active on the forum since July of 2017;

Another regular, contributing member of the forum who has fallen off by the wayside over the last couple of years.

Probably doesn't own his Commander anymore I'm guessing. Either that, or, he has just lost interest for whatever reason.

It's kind of sad to watch the good, contributing, forum members come & go, as the years go by.
 

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We are all not young and at sometime we just go. The other half does not even know we are here. so you never know what happened. Have lost many good contributors and hopefully most just sold there xk.
 

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We are all not young and at sometime we just go. The other half does not even know we are here. so you never know what happened. Have lost many good contributors and hopefully most just sold there xk.
I'm know I'm not the oldest - and I'm certainly not the youngest, I turn 50 in a couple of weeks; I also realize that there are those members like you & @jeep5253, that have been around far longer than I have.

I understand what you're saying though @Creek, I guess we can only hope that at the very least, those who are no longer here, actively posting, are at least still enjoying life - and in good health.
 

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Discussion Starter #11
Where’s Mongo? Yes, the solenoids can go bad. I just replaced one of mine. I was getting misfire codes for cylinder 6. Turning off MDS via tow/haul mode solved the problem temporarily. Replaced the MDS solenoid...no misfires. Personally, I’d ditch the MDS unless you do a lot of commuting. The 09-10 system works much better, but my 06 sucks it down no matter what I do. By the way, I also have the HemiPro. Going strong since 2016 when I lost the factory engine to a dropped valve seat.


Thanks! Great to hear the HemiPro is working good for you. I think I have all the parts together and will be installing it this weekend.


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Im guessing my MDS is no longer functional as i cant seem to ever get the mileage i used to get when i first bought it. Question is, should there be an engine code or something obvious to see, if the solenoids fail?
Also, what is "hemi-pro" supposed to be used for?
 

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Discussion Starter #13
Im guessing my MDS is no longer functional as i cant seem to ever get the mileage i used to get when i first bought it. Question is, should there be an engine code or something obvious to see, if the solenoids fail?

Also, what is "hemi-pro" supposed to be used for?


I do believe you will get a code for failed mds. HemiPro is the engine rebuild company I bought my engine from. Sorry for not being very clear on that it does sound like a programmer or diagnostic devise name!


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Im guessing my MDS is no longer functional as i cant seem to ever get the mileage i used to get when i first bought it. Question is, should there be an engine code or something obvious to see, if the solenoids fail?
Also, what is "hemi-pro" supposed to be used for?
There is a way to hook up an indicator LED to let you know when the MDS is on. There is a write up on how to do this starting here https://www.jeepcommander.com/forums/10-electronics-nav-discussion/10433-m-d-s-what-how-do-i-know-when-active-5.html#post154471
 

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Thanks i had that bookmarked and forgot all about it! If i remember right that just signals power is going to the solenoid. Need to get that done next time i pull wires through the firewall.
 

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Im guessing my MDS is no longer functional as i cant seem to ever get the mileage i used to get when i first bought it. Question is, should there be an engine code or something obvious to see, if the solenoids fail?
Also, what is "hemi-pro" supposed to be used for?
I was getting a misfire code for cylinder 6. After extensive research and testing, I tracked it down to the MDS solenoid keeping the lifter open (or closed?) when it shouldn’t be. Replaced it, no more code. I still get crappy mileage though.
 
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