locating a ignition miss in the engine

Discussion in 'Engine: Repairs and Modifications & generally corv' started by Grumpy, Jun 9, 2018.

  1. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    the idea of using a infra-red temp gun to locate a mis-fire cylinder is useful and valid, a mis-firing cylinder will tend to run cooler, as less hot exhaust gas flow will result, check the cam lift as a worn cam lobe might be the cause.
    Id check the carb float levels and fuel pressure was consistent and replace the fuel and air filter, distributor rotor and cap,
    Id also suggest a basic tune-up and use of a multi meter to verify the ignition wires condition.
    if you post clear color pictures of the labeled by cylinder number spark plugs it could in many cases provide valid useful related info. as always you'll be better off dealing in facts and you get those through isolate and test procedures.
    Id suggest a compression test and adjusting the rockers/and looking for vacuum leaks.
    obviously check your ignition timing and advance curve with a tach and a timing gun, to verify what your dealing with

    Ill post a few related links
    http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products

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    Last edited: Jun 9, 2018
  2. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member


    here above is a picture similar to what many cars headers would look like, a infrared temp gun like the one I linked to is a great diagnostic tool.
    the infrared temp gun is a fast and accurate diagnostic tool, but it shows symptoms,
    and its up to the mechanic to find causes, and that takes diagnostic skill,
    experience and the ability to isolate and test and use logic.
    the temp you see will depend a great deal on engine rpm, compression ratio, fuel/air ratios,
    ignition advance curves and other factors that will change the exhaust gas temps.
    generally they fall in the 450F-700F range ,
    but variations of 40F-60F between cylinders if your looking at individual, header tube temps,
    due too better cooling air flow, on the front cylinders header tubes ,
    ignition timing and fuel/air mix ratio are common, but your looking more for,
    significant variations in header tube temps,
    between different cylinders, they should all be well within 50F-70f
    of each other, if not the chances you have, some other factor causing the change,
    like an ignition wire arcing, or a broken conductor,
    a defective fuel injector,
    restrictive header primary tube,
    a partly plugged catalytic converter,
    bent spark plug ground,
    an intake vacuum leak or
    improperly jetted carb ,
    causing the problem are reasonably high.

    http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
    Last edited: Jul 13, 2018

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