Misfire and poor idle

Discussion in 'Troubleshooting & Diagnosis' started by Bryce Maese, Sep 2, 2021.

  1. Bryce Maese

    Bryce Maese New Member

    Messages:
    19
    Likes Received:
    4
    Joined:
    Apr 2, 2021
    Hey every body,
    I have a 1975 camaro with a 1986 Chevy 350 crate motor with a Holley 650 carb, recently the car has began acting up. One day the car was running perfectly fine, after school I got back in the car and it began to run like crap. By ear I would diagnose it as a misfire but not positive. The car runs unevenly and sporadic, rarely will it idle unless I help it with the throttle. Even the car is drivable. That day I messed with it (didn’t change or replace anything) just wiggled some things and the car fired right up and ran for a week perfectly, it recently did this again this time Regulierung me to get a tow, now I knew something was wrong so I replaced spark plugs (old plugs looked fine) spark plug wires and cap and rotor. After this the car ran great for a day then it began doing it again. This is where I’m stumped.

    my thoughts slash observations:
    The car intermittently working leads down the path of electrical.
    My voltage gauge shows do deviation in voltage though.
    In the dark i saw a slight spark from the alternator (so maybe the alternator is junk) but why would it be making constant power

    If anybody has any ideas or things I can try I would really appreciate it.
    Thanks
     
    Last edited: Sep 2, 2021
  2. biker

    biker Veteran Member

    Messages:
    3,975
    Likes Received:
    1,906
    Joined:
    Dec 7, 2014
    Location:
    Canada
    Start with the very basic stuff when it comes to the charging system. Make sure your battery terminals are tight and clean. I know it's simple and obvious, but so many problems get traced to loose battery terminals, and they do come loose on their own.
    Check connections, including the ground on the alternator bracket.
    When it runs like crap, see if you can get a good meter on the battery to check alternator output. Anything less than 12 volts will make for very poor ignition performance. Should be 14+ volts at idle if it is working properly.
     
  3. Bryce Maese

    Bryce Maese New Member

    Messages:
    19
    Likes Received:
    4
    Joined:
    Apr 2, 2021
    I have checked my battery terminals and there secure, I can check with a multi meter but my voltage gauge shows a good charge and it’s constant
     
  4. COPO

    COPO Veteran Member Lifetime Gold Member

    Messages:
    21,095
    Likes Received:
    2,616
    Joined:
    Sep 15, 1999
    Location:
    Ontario, Canada
    Check ohms reading on spark plug wires. 40 ohms per foot is excellent. The less the better. Check your manufacturer doc what your wires should be per foot.
     
    Last edited: Sep 2, 2021
  5. biker

    biker Veteran Member

    Messages:
    3,975
    Likes Received:
    1,906
    Joined:
    Dec 7, 2014
    Location:
    Canada
    Ok, if your HEI is original, the other thing that goes bad on them is the wires on the pickup coil inside the distributor. You can get a new pickup coil, and it is easy to change, but you have to pull the distributor to do that. At that point, you are better off putting in a good new HEI distributor and keep the original as a spare if needed. You can change the pickup coil on it and put it on the shelf. You may want to use the original HEI module in whatever new HEI distributor you buy. The original GM modules are very good.

    But, try to eliminate everything else you can and diagnose it to the real cause before you fire the parts cannon.
     
  6. Bryce Maese

    Bryce Maese New Member

    Messages:
    19
    Likes Received:
    4
    Joined:
    Apr 2, 2021
    Ok I will check ohms on plugs and maybe ill just drop a new distributor in I have a couple laying around.
     
  7. Bryce Maese

    Bryce Maese New Member

    Messages:
    19
    Likes Received:
    4
    Joined:
    Apr 2, 2021
    Hey guys so here is an update and it isn't a good one. My Camaro now has a brand new distributor wires, plugs, and plug covers. Nothing has changed, the car will fire right up idle great and drive perfectly for about 20 minutes at which time the engine begins to hate life. The car at a stop will barely idle and is supper shaky and jumpy and is trying to die. I put the car in neutral and tried to hold the idle higher but at any low rpm the car has a terrible lurch and presumable misfire. getting going is a struggle, the car bogs and kind of coughs itself into movement, once the car is moving with some rpm its smooth. the second I upshift and decrease the revs it begins to bog, (its like there is a wall in the rpm that it pushes through then goes). I did buy a msd 6al as an upgrade so I will be installing that but I cant imagine that fixing things considering it has a brand new distributor.
    Any thoughts are appreciated thanks ya'll
     
  8. MChamp

    MChamp Veteran Member

    Messages:
    299
    Likes Received:
    78
    Joined:
    Jun 6, 2021
    Location:
    north carolina
    which holley 650? sounds to me like it's loading up..... (and I would put a timing light on each wire to verify its firing before pulling anything apart when it's acting up)
     
    Last edited: Sep 16, 2021
  9. Bryce Maese

    Bryce Maese New Member

    Messages:
    19
    Likes Received:
    4
    Joined:
    Apr 2, 2021
    It’s a Holley 6210, I have had some throttle issues a while back so I thought the same thing so I actually just ordered a Holley brawler a hour ago
     
    MChamp likes this.
  10. MChamp

    MChamp Veteran Member

    Messages:
    299
    Likes Received:
    78
    Joined:
    Jun 6, 2021
    Location:
    north carolina
    before you change carbs,, have you looked into the choke set-up and see if it's working right?
     

Share This Page