Well I am going to bring this thing in. Do you guys recommend bringing it to a dealer or a private shop? Do private shops do OK with the MDS and all that?

 

I'm betting lifter or valve seat. That's how the dropped valve seat on my 4.7 in the Grand Cherokee started, but I had little warning. First I heard the sound was idling but no CEL, just a detectable sound like yours. Backed it out the driveway and before I could shift it into drive to pull off the valve seat dropped and caused utter mayhem.

Have it checked ASAP just in case. Could be as simple as a plug or coil pack but if not you don't want to take the chance of that thing dropping and taking out the engine...

 

Yea, its weird because it eventually goes away and then runs like normal. I am going out of town tomorrow so I am going to bring it to either my buddies shop or a dealer today to have it looked at.

 

If it's under warranty - dealer. If not, if you have a private mechanic you trust, I'd take it there, unless you are really in love with the dealer. If it were me (I've got just a few more miles than you do on yours), I'd swap the coils and see what happens, especially if I couldn't get it in a shop right away. Worse that can happen is you have a new set of coils and still have an issue that needs checking. Next time I change plugs, I'm putting in new coils for peace of mind.

 

Truck was taken on a flat bed to the dealer tonight (free towing with geico). We'll see what happens. A guy in another thread posted up after a couple years :-) he had a video with the exact same sound. He is going to let me know what his solution was. Oh yea, my wife got stuck with a dead battery tonight.... When it rains it pours.
Dealer just called, they are gunna start on it tonight.

 

Well, mechanic said it sounded like it might be the mds solenoid because as far as he could see the ecu wasent telling the solinoid to activate mds at idle. So he then took off the intake and traced the wiring for the mds and couldn't find any shorts or anything out of the ordinary. Took off valve covers and said rockers/springs look good. Bumped the engine with valves off and all looked OK. He said he can't be 100% sure the springs are fine until they get the heads off to check the lifters. So, so far I'm going to be charged 4 hours for all of that including getting the heads off to check the lifters.

He asked how often I did oil changes, I said 5,000 miles, he said never go over 3,000 with a motor with mds lifters.

 

You could have used the came swap thread in our FAQs to use to take everything apart yourself and save some coins......Im just sayin'

 

Your preaching to the choir man. A couple things though, I was heading out of town this weekend and needed my truck for Monday. I have never had anyone do any work to any of my vehicles until this problem, but its my only vehicle right now so I don't have the luxury of taking my time working through it. Plus I'm not going to lie, tearing the motor completely down is intimidating. If I had another vehicle I would have liked to take my time over a couple weeks to do it myself for sure, but I don't have anything else to drive... which is basically why my truck is still 100% stock lol.

 

One or more of the MDS lifters were gummed up and stuck. They are dissasembling the heads, cleaning them and reassembling them. Re-placing the lifters and the MDS solenoids. I also had them use a new MDS wiring harness, the original one had has been sitting under the intake for 90,000 and looked pretty shoddy.
Definitely not a fan of the MDS system.

 

Wow...Any coin you saved (if any) with MDS is shot to hell now...I've the same yr truck and pray this won't happen. I Use Star-tron w/every fill up (a little tip Hammer gave us on this site) and if you use Dino oil 3500k is tops.

I know hind site is 20/20 but swapping coils might of been worth a shot cause it sounds like the mechanic is getting in pretty deep.

But in any case I hope this fixes the issue.