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 Misfires Help Topic Below

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

Low Compression Causing Engine Misfires – Is It A Mechanical Malfunction

Engine Misfires – Finding And Fixing Them The Easy Way

Engine Misfire – 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


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

What causes misfires? Basically, it’s one of three things. Loss of spark, the air/fuel mixture is out of balance, or loss of compression. Loss of spark includes anything that prevents coil voltage from jumping the gap at the spark plug. 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. Or, 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.

Finally, With loss of compression the most likely causes are a leaky exhaust valve or a blown head gasket. 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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