what did I do wrong - jeep liberty

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  #1  
Old 12-14-15, 03:24 PM
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what did I do wrong - jeep liberty

My stepson has a 2002 liberty V-6. He was driving it this weekend when it all of a sudden started running rough and the check engine light came on. Checked the codes and got P0354 and P0304 - coil/plug misfire on cylinder #4.

So today I replaced the sparkplugs and swapped the coils on #1 & #4. I also reconnected a loose vacuum line. Replaced serpentine belt and radiator cap also not that would be relevant. Now it runs worse

new codes;
P0351 - #1 ign coil
P0354 - #4 ign coil
P0300 - multiple misfire
P0301 - #1 misfire
P0304 - #4 misfire
P1299 - vacuum leak
 
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  #2  
Old 12-14-15, 03:40 PM
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Most likely the rocker arm on the intake of cylinders 1& 4 have fallen off. If it is a single overhead cam engine, that is. I have been through it with my Grand Cherokee. It will happen if the lifter becomes too weak to keep the rocker arm in place. Oddly, the rocker arm is not held in with anything but a lifter, axis, and valve. It is not bolted on like our older engines were. Clear the codes first, and if it doesn't settle down, you'll have to remove both rocker covers to see what is up.
 
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Old 12-14-15, 03:54 PM
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While I wouldn't rule out a rocker arm issue, I don't believe that happened on #1. It was firing fine prior to installing new plugs and swapping the coils. I almost have to believe it's coil related but can swapping them out make one that was working go bad? or does #4 have issues other than a bad coil that is causing the misfire?

His jeep has the 3.7 V6
 
  #4  
Old 12-14-15, 05:29 PM
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You were already showing a code on #4. Swapping a bad coil to #1 still allowed the #4 code, PLUS it gave you a #1 code. A new coil on #1 plus clearing the codes may bring things back to normal.
 
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Old 12-15-15, 03:53 AM
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But wouldn't disconnecting the battery have cleared the #4 code? plus the fact that it now shows multiple misfires. I figure I'll swap the two coils back and see if that gets rid of the extra codes.
 
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Old 12-15-15, 04:02 AM
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Does your scan tool allow you to clear the OBD Codes . . . . or do they just accumulate as you re-position questionable components ?
 
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Old 12-15-15, 04:10 AM
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I don't have a scan tool On his jeep you can turn the ignition on 3 times and it will flash the codes. I then got the code definitions off of the internet. Doesn't disconnecting the battery clear the codes?
 
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Old 12-15-15, 04:36 AM
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probably didn't get cleared since there still in there might try leaving it disconnected longer.
probably had a bad coil on 4 but now its in number 1 position could try a spark test on the coil see if it has spark also might check the boot for carbon tracks.
 
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Old 12-15-15, 04:40 AM
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I know almost nothing about OBD but I do know that it takes a specific operation to clear the codes. Disconnecting the battery for a short period of time does not clear codes.
 
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Old 12-15-15, 04:42 AM
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Originally Posted by marksr
". . . Doesn't disconnecting the battery clear the codes? . . ."
That probably varies by vehicle; but it certainly doesn't remove them on my Volvo.

I think the OBD Unit uses an E-PROM type of memory chip that retains the value even when the power supply is removed . . . . but I don't know if that's universal.

My OBD Codes have to be erased or over-written . . . . I always do it before going in for Inspection !
 
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Old 12-15-15, 04:43 AM
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Visually all the coils looked the same. I don't remember if it was 5 or 6 but it was a little damp on the exterior of the tube that extends down - but I probably spilt some coolant when I moved the overflo jug above it.

How do you do a spark test on this type of coil? first time working with this type of set up.


Vermont - depending on how things go today, I might just go buy a scan tool.
 
  #12  
Old 12-15-15, 04:53 AM
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Originally Posted by marksr
". . .depending on how things go today, I might just go buy a scan tool . . .
I am very pleased with the Actron CP9575 that I picked up on eBay . . . . some estranged Wife was cleaning out her Husband's garage. The CP9575 allows you to not only see the Codes; but also delete them. It does not go into great detail explaining each Code; I have to have paper and pencil and go online and get more information . . . . not much of a burden.
 
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Old 12-15-15, 06:46 AM
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Ok, I swapped the coils back, disconnected the battery to reset the codes and now the only code that flashes is P0354 [#4 coil] so as much as I hate replacing parts when I'm not certain that is the issue - I'll go get a new coil. I understand that putting a bad coil on #1 would make it misfire but why didn't the good coil fix #4?

If that fixes his jeep, I'll hold off on buying a scan tool. My wife is already wanting to know what she can get me for Christmas ..... and I haven't even started my shopping yet
 
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Old 12-15-15, 08:59 AM
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Well that was a wasted $30 and trip to town Still get the #4 coil misfire code although it might not be running as rough [haven't test drove it yet] I guess maybe I need to research/trace the wiring to the coil .... and electrical trouble shooting isn't something I'm great at
 
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Old 12-15-15, 10:41 AM
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How long has your stepson owned this vehicle?
 
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Old 12-15-15, 02:32 PM
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He bought it new. It was basically totaled out 8-10 yrs ago but the insurance refused to say so even when the repair bill reached 15k [took dealer over 4 months] although I think I've since repaired/replaced all the things that were missed during the repair.
 
  #17  
Old 12-15-15, 02:55 PM
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It's 13 yrs old, I would just go ahead and replace all the coils since I'm guessing they are the originals and they don't last forever. If you do get a OBD tool look for one that not only retrieves codes but will also give 3 or 4 of the most common fixes for each code.
 
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Old 12-15-15, 06:39 PM
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I am happy with my Autel OBDII/EOB scanner. Not very expensive and will not only give and clear codes, but you can use it with a running engine to see overall performance. I have found if you don't clear the codes as you go, the car will perform in the degraded style, even if you change a component.
 
  #19  
Old 12-21-15, 01:45 PM
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His jeep is fixed!
Replaced the computer with a $50 junkyard one ...... rebuilt ones are $350 and have to be ordered
 
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