Misfire

Discussion in '2005+ Mustang GT 4.6L Tech' started by Kev555, Jun 19, 2022.

  1. Kev555

    Kev555 Member

    56
    10
    My GT has developed a misfire today and I tried some all the software and diagnostic tools I have but the best would only confirm a misfire but not which cylinder. I was able to confirm no faults with injectors on the software and no codes stored. Which software or tool is the best for all in the Stang and the cheapest to buy?
     
  2. DieHarder

    DieHarder Senior Member

    971
    437
    Not sure about the software... However, you can try a low tech method to isolate. Try to listen for which bank then disconnect the connector for the COP's one at a time on that bank and restart (note symptoms) and repeat for each cylinder. Each disconnected COP should yield a change in running rpm. When nothing happens (no change in rpm) after the disconnect you've found it. Would then recommend swapping plugs with another cylinder to see whether the plug/COP or wiring is an issue. Brute force method (and simplest) change all of the plugs.
     
    redfirepearlgt likes this.
  3. Kev555

    Kev555 Member

    56
    10
    Thanks Die Hard I'm just after coming in from trying Forscan but it was the same as WOW software. I guess Due to the mustang setup theres no actual way of viewing oscilloscope data for these with software. I did pull the plus off the COP's one by one as you have already suggested, they all went off the cylinder and lowered the revs ( I had a accelerator wedged at 1500 rpm to but make the miss sound clearer) but 8 wasn't as pronounced as the rest, I'm going out now to swap them COP's over as you suggested to see if it problem moves with the COP, There was a full set of new plugs installed about less than 2000 miles ago by the dealer I bought it off I forgot to add in first post. I will pull them to check if no joy with moving the COP around.
     
  4. Juice

    Juice forum member

    4,081
    1,593
    If you go into mode 6 data with Forscan, you can see each cylinder's misfire count. Having a few is OK. You will see a lot more on the trouble cylinder.
     
  5. Kev555

    Kev555 Member

    56
    10
    Thanks juice I will try that as still not convinced the miss is in cylinder 8 after swapping COP's. I am going to change the fuel filter and run out that tank as well to rule bad fuel or dirty filter, I will try that mode in forscan tomorrow to see if it shows up which cylinder it is.
     
  6. Aussie-Parnelli

    Aussie-Parnelli Junior Member

    26
    15
    Hi
    I bought one of these for my '06 race car, Turned out to be 2 bad COP pigtails
    They are cheap and work
    High Quality Checker Coil On Plug COP Ignition System Quick Tester ADD 750
     
    Kev555 and Pentalab like this.
  7. Kev555

    Kev555 Member

    56
    10
    Thanks Aussie, useful bit of kit
     
  8. Speedracer67

    Speedracer67 Junior Member

    12
    5
    Aussie,
    Could not see link to the COP checker you used.
    Could you send it again?
    Thanks
     
  9. Kev555

    Kev555 Member

    56
    10
    Well at least I found the cylinder with the misfire (thanks to juice for the module 6 tip) and then I found the cause. Some F*** hash of a mechanic that fitted a set of plugs for the dealer I bought it off managed to possibly destroy all the threads in all the plug holes, cylinder 2 is blowing by the plug loosing compression and I tried cylinder 1 and 3 and the plugs seem the same. I couldn't get the plug out of 1 and I dont want to upset 3 anymore . I dont even want to look at the rest of the cylinders ATM. I see nearly all of the 7mm bolts that hold down the coil packs are done with chemical steel paste as well. How in the F*** could anyone make so much of a mess in one job like changing a set of plugs and then leave it like that???
     
    Last edited: Jun 21, 2022
  10. Juice

    Juice forum member

    4,081
    1,593
    Well that sucks.
    Maybe it was a spark plug change from hell, and most of the plugs broke coming out. Still, its no excuse for butchery.
     
    Kev555 likes this.
  11. Kev555

    Kev555 Member

    56
    10
    Yes I read about them two piece plugs from hell Juice so possibly thats the case but ive haven't heard of any needing time serts in the holes if they come out in two pieces? Looks like time certs are the only handy way out for me.
     
    Last edited: Jun 21, 2022
  12. Juice

    Juice forum member

    4,081
    1,593
    Never did any broken plugs, so Im not sure.
    But, I was under the impression the special tool for extracting the broken plug(s) prevents thread damage in the beads.
     
  13. Kev555

    Kev555 Member

    56
    10
    Yes that seems to be the impression from most mustang websites ive viewed threads on this subject
     
    Last edited: Jun 21, 2022
  14. bambam 06

    bambam 06 Member

    65
    11
    Apparently he used a drill bit. I'd be speeding to that dealer to see the owner.
     
  15. Kev555

    Kev555 Member

    56
    10
    ?? dont get that one sorry
     
  16. Speedracer67

    Speedracer67 Junior Member

    12
    5
    Key to getting the plugs out is to use an impact wrench to take them out. the rattle of the wrench breaks them loose so they don't come apart. Plenty of YouTube videos showing how to do it and also how to use the special tool to get the bottom piece out when they do come apart. Sometimes they do break. Never-seize on the new plugs helps on the next plug change too.
    been there and done that !!!
     
    MrBhp likes this.
  17. djr_xr7

    djr_xr7 Junior Member

    2
    0
    Just recently changed plugs on my 06 GT after getting more and more frequent misfire. Don't know when if ever they were previously changed. I tried all the tricks suggested on YouTube videos - soaking with carb cleaner/penetrating oil/etc, loosening small amount then tightening, loosening, tightening repeatedly. Only 1 came out in 1 piece, the rest felt like they were going to separate. After a couple days of soaking loosening tightening, I tried a little more torque and broke one. Ordered the Lisle 65600 kit and proceeded to break another couple plugs off. Decided I had nothing to lose and tried the impact on a couple which also broke. The Lisle kit got 6 of the 7 tips out before the threads on the puller were too damaged to grab the last one. I was able to order just the puller and got the last one out. None of the plug threads in the heads were damaged at all, so I don't understand how the dealer tech managed to damage yours.
     
  18. DieHarder

    DieHarder Senior Member

    971
    437
    Worth changing to one-piece plugs. Brisk and I believe Champion also make a one-piece plug for them. Brisk is the most expensive but if you're running FI worth it. I run Brisk and break them loose/clean every year to be sure they don't seize. Use a little anti-seize as well. When I first did mine the previous owner never had them changed. Broke three getting them out. Lisle tool is a life-saver.

    You might want to try chasing the threads before getting into more expensive fixes. Hard to believe someone could "F" up that bad just replacing plugs.
     
    Kev555 likes this.
  19. bambam 06

    bambam 06 Member

    65
    11

    The mechanic used a "Drill bit" to remove plugs, thereby ruining the plug threads. Either way the dealer is responsible. Go there ASAP.
     
    Kev555 likes this.
  20. Pentalab

    Pentalab forum member

    4,741
    836
    Brisk plugs are the real answer. Never seize goop comes in 2 x versions. Regular and marine grade. The marine grade will handle more heat. Make damned sure the new plugs are gapped correctly.
     
    Kev555 likes this.
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.