2012 Misfire under load
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Registered User
Joined: Apr 2017
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So, here we go....
Pulled the intake. Changed the MDS solenoid. Actuation test confirmed that it wasn't working, so no money lost.
Test drive. All is well for a few minutes. Then check engine, and misfires commence.
Changed plugs. They needed to be done anyway. Engine more peppy, until misfire commences again.
Finally pulled the valve cover. No busted springs, but sure enough, the intake rocker on Cyl #7 is moving quite a bit less than the other rockers. Is this a death sentence for the camshaft? Or could there be something in the MDS system that is causing the lack of rocker movement. Obviously, I'd really rather not have to change camshaft and lifters, so I'm grasping at straws.
So now we sit inside, lick our wounds, and try to come up with a new plan of attack.
Any and all help would be appreciated.
Pulled the intake. Changed the MDS solenoid. Actuation test confirmed that it wasn't working, so no money lost.
Test drive. All is well for a few minutes. Then check engine, and misfires commence.
Changed plugs. They needed to be done anyway. Engine more peppy, until misfire commences again.
Finally pulled the valve cover. No busted springs, but sure enough, the intake rocker on Cyl #7 is moving quite a bit less than the other rockers. Is this a death sentence for the camshaft? Or could there be something in the MDS system that is causing the lack of rocker movement. Obviously, I'd really rather not have to change camshaft and lifters, so I'm grasping at straws.
So now we sit inside, lick our wounds, and try to come up with a new plan of attack.
Any and all help would be appreciated.
Captain
Joined: Mar 2012
Posts: 597
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Sorry to hear Mike. Just went thru it. I would count on camshaft and lifters......Dodge was out of stock and parts on back order until who knows when in my area. No good used engines to be found either.
Here is a thread I did in case you havent seen it. Cyl 7 as well. Lol
https://dodgeforum.com/forum/4th-gen-ram-tech/419170-hemi-camshaft.html
Here is a thread I did in case you havent seen it. Cyl 7 as well. Lol
https://dodgeforum.com/forum/4th-gen-ram-tech/419170-hemi-camshaft.html
Registered User
Joined: Sep 2005
Posts: 2
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From:
Been thinking about your issue a little more...as I just went thru diagnosing and replacing a camshaft in a 2011 5.7.
Again I highly doubt mds solenoid failure. When MDS solenoids activate, oil pressure is blocked to the appropriate lifters. The lifter bleeds down to the point where the valve will not open and the lifter basically just goes for a ride around the cam lobe. You could try driving the truck and manually shift gears without going to top gear. It is my understanding that MDS will not activate until high gear. If you still get a misfire at 3800 rpm in 3rd gear for eg. That would eliminate this cycle of the mds.
Now if you had a stuck MDS solenoid always blocking oil pressure to lifters I would think you would get a misfire well under the 3800 rpm.
Again I highly doubt mds solenoid failure. When MDS solenoids activate, oil pressure is blocked to the appropriate lifters. The lifter bleeds down to the point where the valve will not open and the lifter basically just goes for a ride around the cam lobe. You could try driving the truck and manually shift gears without going to top gear. It is my understanding that MDS will not activate until high gear. If you still get a misfire at 3800 rpm in 3rd gear for eg. That would eliminate this cycle of the mds.
Now if you had a stuck MDS solenoid always blocking oil pressure to lifters I would think you would get a misfire well under the 3800 rpm.
