When misfires occur, performance suffers, along with fuel economy, emissions and idle quality.

So, for your engine to fire its cylinder properly, it relies on, three main components.

Consequently, 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. And, it won’t start the chain reaction, that leads to a well-running engine.

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

  • Loss of spark.
  • The air/fuel mixture, is out of balance.
  • Loss of compression.

Loss Of Spark

  • Worn fouled or damaged spark plugs.
  • Bad plug wires.
  • A weak coil.

The air/fuel mixture, is out of balance.

“Lean misfires” can occur when the air/fuel mixture, is too lean to burn. Usually, caused by, a dirty, clogged or inoperative fuel injector. Also, air leaks or low fuel pressure, because of a weak fuel 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.

Loss of compression

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 also likely the head gasket is the culprit.

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

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