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Discussion Starter #1
Ok, this is one for the record and the pros...

Very well maintained, 130k reached and...

PO306 - Misfire on Cyl #6 . (one of 4 MDS cylinders)

I swap the coil with another cylinder. No change. - Coil eliminated.

It goes to the shop.

Change fuel injector - No change. Fuel injector eliminated.

Shop replaces all lifters (using redesigned hellcat lifters), CAM as most-likely candidates according to Chrysler. Balve job on both heads (since it was apart).

Cleans and flushes oil passages. Checks VVT solenoids and MDS solenoids (replaced #6 MDS sol.).

Get car back less an ungodly amount of money from my now empty wallet...

Car seems to run fine, but 1 week later; PO306 returns.

WTF?

Back in shop for a week and no word on anything yet.

This shop has been excellent up to this point.

Comments? Advice? Similar experiences?

Thanks!
 

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From the 'JOIN DATE:' I'd assume the car is a 2005 model which has high tension wires.
Try replacing #6 's HT lead to see if the miss goes away.
If so, with a 130K on the clock, replace them all to avoid similar problem(s) in the future.
 

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Discussion Starter #4
When I joined, I had an 05. That was replaced with this 2011. No wires. Just the twin coil pack which was the first thing I did; swap with another cylinder. No change. Put new plugs in the cylinder; no change.
 

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Misfire - meaning it sometimes fires, sometimes does not? What does (or did) the plug look like - any different wear than the others? I assume the plugs were swapped out with that amount of work.
 

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Discussion Starter #6
Plugs looked fine. I think it is MDS-related, but I don't know exactly how. One minute it runs fine. The next, it shudders and throws the code. Went for a week with no problem and then it's back. Strange.
 

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Discussion Starter #7
Does anyone familiar with MDS think that this could be caused by a piece of debris in the oil passages to the MDS solenoids?
 

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And you are using the required 5W20 engine oil?

What is the engine oil pressure when the DTC pops up?
 

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Discussion Starter #9
Yes, Mobil 1 - always. Not sure of oil pressure at the time, but this problem is always just with cylinder #6 . If pressure dropped off, then I guess there would be a check-engine and code thrown as well as hearing all the other lifters clacking as they pumped down.

Some time ago, the VVT control screen fell apart and the control needed replacing. That was all done and it worked fine, but I am wondering if a piece of debris got caught in the MDS oil path and it intermittently pops into a place where it blocks the flow to the MDS lifter and at other times, it is out of the way somewhere. This is all I can come up with to explain what is happening because everything is either new or it has been checked by swapping with another cylinder.

I just don't know where in that oil path something could be hanging around. That would have to be somewhere between the MDS solenoid for #6 and the lifter for the MDS controlled valve, ** if I understand ** how this works.

The only other thought is something electrical. I take it that the ECU commands MDS on and off via the solenoids, so perhaps a wire on the plug for the MDS solenoid is bad/corroded/loose?

I'm open to any thoughts on this.

Thanks!
 

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Discussion Starter #10
For anyone interested... I am told the problem turned out to be the sonic welds on the composite intake manifold and a collapsing vacuum hose to the PCV valve. Apparently the manifolds go bad over time and then need to be repaired or replaced.

The way to diagnose a manifold issue is to monitor the fuel usage on the head with the misfire vs the head without it. More fuel = intake leak as I was told.

Repair of the manifold showed equal demand on both heads.

Not even a Chrysler mechanic could figure this out. The hint came from another shop up the street who said that these (expensive) manifolds are notorious for failed sonic welds.
 

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Thank you sir for getting back to us on the resolution of your problem. So many of the issues presented to us are left open leaving us wondering what ever became of old "whatshisname"

As is, it sounds a bit of good luck that you got the right tip at the right time. We have learned plenty from your thread, at least I have. ::smile::
 

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Discussion Starter #12
You're very welcome. I was also told that in the process there was an ECU firmware update that I was never notified of, so they flashed it and that cost a bit, but I notice the "ECO" (MDS?) indicator going on and off much more often and quickly too, as well as a change in the pedal response. Before, pressing the go pedal with the slightest pressure made it fly. Now it is much more tame, but of course, it roars ahead like a rocket when I put my foot in it to pass on the highway.

I've put a couple of hundred miles on it and so far... so good. I hope it stays that way. :)
 
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