Misfires - Are Caused By Loss Of Spark, Compression Or Air/Fuel Mixture
Misfires – Are Caused By Loss Of Spark, Compression Or Air/Fuel Mixture

Choose Your Help Topic Below

Engine Misfire Causes – Fuel, Ignition, Coolant Or Compression Related

Low Compression – Is It A Mechanical Malfunction

Engine Misfires – Finding And Fixing Them The Easy Way

Engine – Rough Idle On GM 4.8L, 5.3L, 6.0L Engines

Misfire Issues – Causes – Symptoms – Diagnosis – Potential Damage

Mechanical Engine Misfires – What Are They – How To Find Them

Engine Misfiring – What Can Cause It – Tracking Down The Problem

Rocker Arms Dislodging – Along With Valve Seats Falling Out

Engine Hesitation – What Is It – What Can Cause It – Diagnosing It


When misfires occurs; performance suffers along with fuel economy; emissions and idle quality.

So, What causes misfires? Basically, it’s one of three things:

  • Loss of spark; the air/fuel mixture is out of balance
  • lack of compression.
  • Loss of spark

Causes include worn; fouled or damaged spark plugs. Bad plug wires or even a cracked distributor cap.

Consequently, A weak coil or excessive rotor gap; inside a distributor would affect all cylinders; not just a single cylinder.

“Lean misfires” can occur when the air/fuel mixture is too lean to burn. Usually, Caused by a dirty; clogged or inoperative fuel injector. Or, Air leaks or low fuel pressure; because of a weak pump. In addition; A restricted filter or leaky pressure regulator.

But, Low fuel pressure would affect; all cylinders rather than an individual cylinder. A leaky (EGR) valve can also have the same effect as an air leak, causing a misfire.

So, for your engine to fire its cylinder, it relies on three main components. Because, it needs fuel to burn, oxygen to facilitate the burn reaction, and a spark to get things going. If any of those elements are not present at the perfect time, the cylinder won’t combust. It won’t start the chain reaction that leads to a well-running engine.

Finally, With loss of compression the most likely causes; are a leaky exhaust valve or a blown head gasket. So, If two adjacent cylinders are misfiring; it’s likely the head gasket. Also, if an engine is overheating or losing coolant; it’s likely the head gasket is the culprit.

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