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Thread: Gen II stumbling/stuttering during acceleration

  1. #1

    Default Gen II stumbling/stuttering during acceleration

    Hi guys,

    This morning on the highway I was doing about 100 km/hr and went to overtake. I was in 6th gear and when I accelerated the engine stumbled/stuttered quite badly and I also heard a fluttering noise from the engine bay. When it was carrying on I could tell it lost power and I could feel the thumping through the car.

    I backed off and then resumed accelerating slowly and all was fine, and the car behaved itself for the rest of the drive to work.

    Sometimes I get some minor stumbling in the higher gears when accelerating but nothing like what happened this morning.

    Any ideas? Car is stock engine wise, only other mods are rmm and ssp. Has 24,000km on the clock.

  2. #2

    Default

    i have a 6 , have seen this happen
    a: tmic heat soak- traffic stand still etc
    b: colder then normal weather
    c: some times randomly!
    BUT when i go to try again, same as you i get no problems...

  3. #3
    Join Date
    Apr 2010
    Location
    Canberra
    Posts
    9,459

    Default

    I'm going to go with one of the following 3 things:
    1) spark plugs
    2) hpfp needs replacing
    3) some sort of boost/intake leak

    Hard to tell without some way to get logs though

  4. #4

    Default

    Yeah its hard without logs, its stock so I don't have anything like an accessport.

    I tried to replicate it during the rest of the drive but no go. So that means if I take it to Mazda or the usual place I go to I'll be paying for them to stuff around and then tell me 'can't replicate problem'. Ugh.

    Sort of feels like a fuel pump (had one let go in my V8 and the missus Barina and it felt similar) or plugs (had a misfire in the same V8 and it also felt similar).

    Random stumbling also happens, usually in 4th, 5th and 6th when accelerating.

  5. #5
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    Apr 2010
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    Canberra
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    Default

    Usually low down in the rev range?

  6. #6

    Default

    Yes I think so.

  7. #7

    Default

    mine happens probably when boost comes on / full boost comes on

  8. #8
    Join Date
    Apr 2010
    Location
    Canberra
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    9,459

    Default

    Quote Originally Posted by Brissy_MPS3 View Post
    Yes I think so.
    If it's low down, and when accelerating heavily, probably hpfp
    Quote Originally Posted by skeetskeet View Post
    mine happens probably when boost comes on / full boost comes on
    Probably spark plugs...
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
    3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings

  9. #9

    Default

    Quote Originally Posted by SarcasticOne View Post
    If it's low down, and when accelerating heavily, probably hpfp
    Really, on a stock car?

    It does feel like a fuel delivery issue though.

  10. Default

    Quote Originally Posted by SarcasticOne View Post
    I'm going to go with one of the following 3 things:
    1) spark plugs
    2) hpfp needs replacing
    3) some sort of boost/intake leak

    Hard to tell without some way to get logs though
    ^THIS (in bold/underline)

    Get yourself to a rolling dyno & ask them to check fuel pump booster. Happened to my car early on. Replaced, never a problem since. Keep old pump if modding, get new internals. I didn't keep mine.
    3 MPS - Rolling on Pirelli PZero Neros, sitting on Bilstein B12's, stock internals... still makes me smile with the Zoom Zoom.

  11. #11

    Default

    So would be a warranty issue then?

  12. #12

    Default

    does a whining noise like a high pitch one, mean hpfp as well?

  13. Default

    Haven't heard a high pitched whining noise before... except for my wife when I say I'm going out for a drive!

    - - - Updated - - -

    Quote Originally Posted by Brissy_MPS3 View Post
    So would be a warranty issue then?
    One would think, but mine was out of warranty (went about 6 months out of warranty... ).
    3 MPS - Rolling on Pirelli PZero Neros, sitting on Bilstein B12's, stock internals... still makes me smile with the Zoom Zoom.

  14. #14

    Default

    Have you waterblastered the engine lately?

    I had a similar issue, felt like a rod snapped at times, I had cleaned the engine and water was in the spark plug ports, dried it out, pulled the plugs and cleaned them with a wire brush, did a coil spring stretch and cleaned map sensor plug contacts. Fixed!

    Sent from my HTC One X
    Last edited by 1CMS1; 21-03-2014 at 05:34 PM.

  15. #15

    Default

    Fuel pump is possible but I think it is more simple.

    You may well find it is a combination of high BAT's due to low airflow highway driving, at low rpm's, and a small boost surge that the boost controller tries to reign in.

    The combination of these two things will make the PCM pull timing, and close off the throttle plate, to control boost spike and KR.

    This is especially prevalent when partial throttle boosting, say for hills or overtaking, after a period of time travelling at something like 100km/h.

    It would still be worth checking your fuel pump out, since a faulty hpfp is a death sentence on our cars, but I personally think it is more a quirk of Mazda stock tuning, since the oem tune is not great.
    MPS is gone. Ghey Trail enabled....Not Happy. MPS 6 to come

  16. Default

    Had this 3 times previously.

    Cracked porcelain on the spark plug #1
    Each time were less that a thousand km's and one step colder.

    Cause of this was total and utter crap factory earth system.
    Solution... Add additional earth straps to block.

    First check would pop the plugs out, visual inspection of porcelain. Second check would be spark plug gapping.
    The plug gap is probably my guess in your case.

    If plugs check out... Then get HPFP checked out.
    Possibly download torque app on your phone with an elm327 obd reader. Monitor your HPFP pressure for like $30

    Its not the greatest... But does the job if no cobb AP

  17. #17
    Join Date
    Aug 2011
    Location
    Sydney North
    Posts
    441

    Default

    ^^^ what he said. I exactly the same. Ran 3 new earth cables all fixed. Thought it was cracking the spark plugs, thought it was the coils. It was a shitty earthing system

  18. #18

    Default

    Can you guys post pics of your extra earth connections? And more specifics? I have heard extra earths have good benefits

  19. #19
    Join Date
    Aug 2011
    Location
    Sydney North
    Posts
    441

    Default



    3 new earths off the battery to various places and 1 new earth from engine to chassis. All factory earths still in place

  20. #20

    Default

    What grade cable?

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