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Discussion Starter #1
Hi all

hoping you can advise on a long standing problem I've got with my 2007 with 5.7 Hemi.

The problem is with a misfire which neither the dealer or local independent can resolve, its been going on for 2 years, I will describe what the symptoms are and what has been done so far.

Symptoms first. -

  • Basically the misfire occurs at low revs, low throttle opening, low load conditions. but it is intermittent (I can replicate it pretty much when I want too)
  • it occurs both on Petrol and LPG in the same way,
  • if you kick-down, it clears up,
  • if you take it out of drive(D) and put it in 3or2 it clears it (higher revs?).
  • it is more noticeable when the MDS is active but not always, I have an MDS light installed so I know when it is active.
  • I think it occurs more in warm weather (I live in the UK so it is never that Hot!)
  • It does not miss-fire when the engine is cold
  • I think it does it more when the kids are in the back seats! - no, seriously!
  • Most of the time I can replicate the problem when driving at 30mph with 1k revs and I slightly feather the throttle
  • I have never had a DT light come on or had a code to retrieve
what I have done:

  1. changed all 16 plugs for double iridium
  2. bought a coil pack and methodically moved it around all 8 cylinders
  3. Taken it to the local Jeep dealer who acknowledged they could feel the intermittent misfire but could not diagnose it! the recommended I let it get worse so they could find it!
  4. same reply from a local jeep independent garage.
I have a proper manual to work through diagnostics, but any advice anybody has on where to start would be great. does anybody have a complete schematic for the engine management system (sensors, connections etc.) and for the Ignition system as well. the manual does not have an overview of either system.

All help advice will be very welcome

cheers

Jim
 

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Discussion Starter #3
yes I used these plugs before fitting double iridium, I changed plugs from copper to try and resolve my issue

thanks for the post though

cheers

jim
 

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To see if it is related to the MDS, turn off MDS by turning on the "Tow/Haul" button
 

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Discussion Starter #5
thanks I will try this tomorrow, does tow/haul just keep the autobox out of high like taking out out of drive? or does it also impact ignition and fuel controls?
 

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All I know is it keeps it in one lower gear and the MDS does not kick in. It may also keep in each gear longer before shifting. It may affect other things but do not know what.
 

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jcasey007; you asked about an '07 5.7 HEMI, but your signature says you have an '06 5.7 HEMI. Which is it? This is important to the last couple of posts, since the '06 was not available with MDS.
 

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jcasey007; you asked about an '07 5.7 HEMI, but your signature says you have an '06 5.7 HEMI. Which is it? This is important to the last couple of posts, since the '06 was not available with MDS.
The 2006 Commander's with HEMIs DO have MDS. Please don't comment on things you know nothing about.
 

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Long shot but maybe try seafoam in your gas tank or something that can clean off your injectors and plugs also any build up that could be on or around the valves it could be predetonation..... maybe try a higher grade of gas... 93 octane
 

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It would help if you could see if it was just one of the cylinders misfiring or does it travel across the firing order. Knowing this would help in which direction to begin diagnosis. If it is across the firing order then you may have a control issue (possible bad connector somewhere giving too much resistance value from corrosion).
If it is one cylinder, then you can check the related items for that piston (fuel injector, coil pack, connections to the pack, connections from controller to pack... etc..
Once a season I disconnect (one by one) all of my engine components and clean the connectors out with a toothbrush and spray with electronics cleaner. I will ensure all connectors have nice clean shinny tabs before I reinstall.
After owning a cherokee, I have become paranoid with connectors and corrosion... It will drive the controller wonky!!!
That would be a first thing to do really to remove variation that bad connections will do. After that then we could look deeper.
By the way, what kind of shop are you at that cannot plug a monitoring machine to the vehicle and give you direct info on the running of the motor? I can do this at home with my programmer.
Buy one of the many computers out there (Diablo Intune ect...) and set that vehicle to the fuel you will use the most, they even option the MDS out if you want.

Dave

Hope this gives you a start, seems like the car is drivable.
 

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Discussion Starter #11
thanks all for the advice,


  • yes its an 06 with MDS but registered in 07
  • Yes I tried higher octane fuel. I find that when we holiday in southern Europe in the summer, it is worse, so last year I tried higher octane fuel, slight improvement, but this would be masking an underlying issue as for 3 years she ran fine on standard and with LPG which has a lower octane value
  • I have not done the disconnect one cylinder at a time, to be honest I've been putting off doing this :) I will do it this week
  • I have a DTC reader, but I guess this is different to a diablo itune. I assume this is a windows program with an interface cable?
you are correct she starts on the button, idles cleanly, pulls well except for this bloody low down miss-fire

will report back on tests this week

cheers

Jim
 

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Discussion Starter #12
looking at the cost of a Diablo Intune I will do all my manual tests first, the main reason for getting one (for me) would be the data logging and display software on the PC, does anyone know of a good tool just to do this ODBC2 logging ?
 

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The 2006 Commander's with HEMIs DO have MDS. Please don't comment on things you know nothing about.
Hmm. How very mature of you, jeep5253.
Maybe you can shed some light here for us all then, because my '06 Limited HEMI does NOT have MDS, and my Chrysler dealer told me that it was not available on the Commander until Late '07. And they expressed their frustration at this, since MDS was available on several other models in '06.

So, if you know more about this then why don't you tell us all what and how, instead of just throwing-out offensive "STFU's"?
 

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Hmm. How very mature of you, jeep5253.
Maybe you can shed some light here for us all then, because my '06 Limited HEMI does NOT have MDS, and my Chrysler dealer told me that it was not available on the Commander until Late '07. And they expressed their frustration at this, since MDS was available on several other models in '06.

So, if you know more about this then why don't you tell us all what and how, instead of just throwing-out offensive "STFU's"?
All Commander HEMIs have MDS. The dealer is wrong. As discussed here in the forum the dealers do not know everything about the vehicles they sell. Hell, I have had to school them on a few things as have other members here. I have a 2006 HEMI with MDS and I have been a member of the forum since 2006. I pretty much know everything there is to know about the Commander. If you don't want to believe me that is your choice. But if you have a 2006 HEMI it does have the MDS. Try googling 2006 HEMI mds system.
 

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Jeep 5253, what do you know about LPG?

Mentioned in the first post was he could run his commander on LPG (liquified petroleum gas?). Was this option available stateside? How much space did it take up?
 

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Discussion Starter #16
Mine was an aftermarket fitment, you really can't tell the difference in performance with normal road driving, the MDS even works!

I have a 100 litre tank (that takes 80 Litres of gas) which replaces the spare wheel underneath.

with our cost of petrol in the UK, LPG is a real winner here (Petrol is $7.20 a gallon, compared to LPG at $4.00 a gallon)
 

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If I understand it correctly; you are NOT getting PCM fault codes indicate any misfires? At least for the U.S. versions, you don't need a code reader to check for misfire fault codes, doing the key dance will show fault codes for misfires, they should light a Check Engine Light (CEL) as well, if you experience more than a couple of misfires.

Have you considered you have a problem that causes engine vibrations that "feel" like a misfire but are NOT actual misfires? The way the PCM recognizes misfires and sets a code is when it notices an uncommanded/abnormal change in crank speed. Some vehicles PCM's have been oversensitive and will set a misfire code for things that aren't misfires, but I have NOT heard of a PCM failing to set a misfire code for a true misfire, at least NOT on any of the Commander engines.

Did this happen before the LPG retro-fit? If NOT have you considered something with the LPG system is causing the symptoms?

You might want to search the forum, there is a few threads about stalling and rough idle on earlier Comander's with Hemi's. It turned out to be faulty PCM, bad connectors in the PCM that made faulty circuits. Simply replacing the PCM was the cure.

Perhaps check over the front Crank Damper, maybe even take off the belt and check all the accessories. Could have a harmonic on rotating assemblies that hits at a certain rpm. AC Clutch's/Pulley's are pretty massive, as well as the full rotation mass of the alternator, something wrong with those that causes a harmonic vibration might only be noticeable at certain RPM's.
 

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Mine was an aftermarket fitment, you really can't tell the difference in performance with normal road driving, the MDS even works!

I have a 100 litre tank (that takes 80 Litres of gas) which replaces the spare wheel underneath.

with our cost of petrol in the UK, LPG is a real winner here (Petrol is $7.20 a gallon, compared to LPG at $4.00 a gallon)
Thanks for the information. A dual fuel system could make my commute cheaper, and provide extra outback range.
 

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Discussion Starter #19
Hi Mongo, thanks for the feedback, your correct not CEL has ever been lit.

I had the LPG conversion on for 2 years before the issue started and it does it on both LPG and Petrol (common component)

I does not do it all the time and a good stab of the go pedal will 'clear its throat' even before revs pick up.

I've bought a OBD2 Logger which will be delivered tomorrow, it was one of the features I read about the Diablo Intune but its $50 and only does logging. so will report back on what the sensors are telling me during the 'miss fire' if it is a miss fire.

it does not feel like a harmonic but at this stage I will check anything

cheers

jim
 
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