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very slight lurching with constant throttle

Discussion in '308/328' started by ndnguyen, Oct 18, 2013.

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  1. ndnguyen

    ndnguyen Karting

    Jul 27, 2005
    166
    #1 ndnguyen, Oct 18, 2013
    Hello,

    My car is an 86-328, recently it is not running right. At idle regardless of hot or cold the engine sound is difference than before, it has more of a base note to it. With constant (or very gentle acceleration) throttle the car has a very slight lurch(buckling/pulsating) under load. Easiest to notice is to maintain constant throttle in third gear while climbing a hill. There's seem to be sound of "soft" misfire during these lurching events. Everything is fine during medium to hard acceleration. The lurching problem seems to occur after the engine is warm/hot though I am not 100 % sure yet.

    I replaced spark-plugs and checked the extenders for pin-holes. Many thanks for any suggestion.

    Nguyen
     
  2. Iain

    Iain F1 Rookie

    Jan 21, 2005
    3,320
    UK
    #2 Iain, Oct 18, 2013
    Sounds most likely to be ignition related & basically a misfire.

    If you checked the extenders then the next thing I'd do would be check the distributor caps & rotor arms & plug leads for continuity (for which you will need to take the Dizzy caps off).

    Another possibility is one of the ignition amp modules on top of the coils starting to go.

    You could also start checking/cleaning electrical connections on the engine wiring loom
     
  3. jjdt

    jjdt Karting

    Apr 3, 2013
    148
    Cape Town
    Full Name:
    Jan du Toit
    #3 jjdt, Oct 23, 2013
    Had the same problem with my 84 QV and changed an extender and plug leads, now it is running super smooth. Considering the age, I am not surprised the leads went. One of the most satisfying fixes to date.
     
  4. vaccarella

    vaccarella Formula 3

    Apr 16, 2011
    2,291
    Full Name:
    Paul
    #4 vaccarella, Oct 23, 2013
    Nguyen, I suggest you check all your extender resistances with a simple multimeter. You may not be able to see damage.
     
  5. ndnguyen

    ndnguyen Karting

    Jul 27, 2005
    166
    #5 ndnguyen, Nov 5, 2013
    Finally with the aid of a timing-light, I found the problem. Spark plug number 1 wire was flakey. I removed the wire again and retested it while twisting it every which way and saw the intermittent discontinuity. I made up quick&dirty replacement spark plug wire, installed it and she purred!

    Nguyen
     

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