[solved] on going cylinder 4 misfire

Discussion in 'Mazdaspeed 3/6 Engine' started by jesus, Apr 2, 2021.

Watchers:
5 users.
  1. jesus

    jesus Greenie Member

    Joined:
    Aug 20, 2020
    Posts:
    37
    Trophy Points:
    8
    Location:
    Colorado
    Ratings:
    +10 / -0
    For the longest now ive been having a cylinder 4 misfire that will come and go out of random. Ive gone through and replaced a ton of hardware( spark plugs/coil packs/wiring harness/fuel injectors and seals/ fuel rail and injector harness/) only time I've noticed a difference of the problem becoming less frequent is when gaping cylinder 4 to around .23-.25 anything higher then that and it seems to just hate it and starts acting up. At a loss here and any info or advice would be greatly appreciated. Data logs can be provided as well if needed.
     
  2. Raider

    Raider Administraider Administrator Platinum Member

    Joined:
    Jan 28, 2016
    Posts:
    7,045
    Trophy Points:
    113
    Location:
    Behind a Keyboard wearing full body armor
    Ratings:
    +8,148 / -12
    Compression and leak down test is next.
     
    Raider, via an iPhone, Apr 2, 2021
    #2
    • Like Like x 1
  3. Awafrican

    Awafrican Moderator Gold Member

    Joined:
    Feb 11, 2016
    Posts:
    3,587
    Trophy Points:
    113
    Location:
    Canada
    Ratings:
    +2,852 / -11
    As raider said.

    But why are your gaps .23-.25" they should be 026-.028"
     
    Awafrican, via a mobile device, Apr 2, 2021
    #3
    • Like Like x 1
  4. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

    Joined:
    Feb 11, 2016
    Posts:
    3,233
    Trophy Points:
    113
    Location:
    Earth
    Ratings:
    +3,532 / -19
    I hope that was a typo
     
    Easter Bunny, via a mobile device, Apr 2, 2021
    #4
  5. jdr767

    jdr767 Greenie Member

    Joined:
    Apr 24, 2017
    Posts:
    219
    Trophy Points:
    43
    Location:
    Garland, TX
    Ratings:
    +115 / -0
    You've done the "bunny hop" with the plugs and boots and kept track? ie: plug from 4 goes into cylinder 2, boot goes on cylinder 3 and make sure the problem stays on cylinder 4?
     
  6. Awafrican

    Awafrican Moderator Gold Member

    Joined:
    Feb 11, 2016
    Posts:
    3,587
    Trophy Points:
    113
    Location:
    Canada
    Ratings:
    +2,852 / -11
    Me too
     
    Awafrican, via a mobile device, Apr 6, 2021
    #6
  7. jesus

    jesus Greenie Member

    Joined:
    Aug 20, 2020
    Posts:
    37
    Trophy Points:
    8
    Location:
    Colorado
    Ratings:
    +10 / -0
    Finally got some free time and was able to find, after a some diag the root of the issue, the ground wire pin for cylinder 4 was completely pushed into the connector causing it to short out the spark. I went ahead and changed out the engine harness with one i had laying around and it hasn't misfired yet ever since then. Also in response to the plug gap i meant .26

    Compression 165-150
    1 - 160
    2 - 165
    3 - 150
    4 - 150
    Leak down 5-15%
    1 - 10
    2 - 5
    3 - 15
    4 - 10
     
    Last edited: Apr 12, 2021
  8. Awafrican

    Awafrican Moderator Gold Member

    Joined:
    Feb 11, 2016
    Posts:
    3,587
    Trophy Points:
    113
    Location:
    Canada
    Ratings:
    +2,852 / -11
    .26" is waay to big, should be .026-.028"

    Glad the misfire is gone, engine seems to have had better days
     
    Awafrican, via a mobile device, Apr 12, 2021
    #8
  9. jesus

    jesus Greenie Member

    Joined:
    Aug 20, 2020
    Posts:
    37
    Trophy Points:
    8
    Location:
    Colorado
    Ratings:
    +10 / -0
    update to this whole mystery it ended up being a improper seating intake valve. I ended up putting some work into the head getting new oem valves, crower springs & fresh seals since then no more cylinder 4 misfire. even went ahead and slapped on the BNR S4 i had waiting around.
     
    • Like Like x 2
Loading...

Share This Page

Users Viewing Thread (Users: 0, Guests: 0)