Low Compression, Causing, Engine Misfires, Is It A Mechanical Malfunction

Low Compression, Causing, Engine Misfires, Is It A Mechanical Malfunction
Low Compression, Causing, Engine Misfires, Is It A Mechanical Malfunction

Firstly, low compression can be caused by a number of different issues resulting in engine misfires.

Secondly, let’s say you have ruled out ignition and fuel delivery, as the cause of the engine misfire.

Consequently, that leaves low compression as the underlying cause of the engine misfire. However, there are many reasons why, low compression might exist in your engine.

Sometimes, there will be low compression in just one cylinder and other times; there will be low compression in all cylinders. You just have to understand the main possible causes and then, fix or replace whatever is damaged.

Consequently, one of the best ways to prevent engine misfires from occurring in the first place is to; perform adequate car maintenance.

This kind of failure is easy to check, using a compression tester.

Testing For Low Compression
Testing For Low Compression

So, if no compression is present, in any one or more cylinders, it means a mechanical malfunction has occurred.

Consequently, misfires that turn on the check engine light and log a cylinder-specific fault code, are the easiest to diagnose. The OBD-II system will identify the cylinder(s) that are not contributing; their normal dose of power and set a code.

Causes Of, Low Compression, In One Cylinder:

  • Carbon Deposits On Intake Valves/Valve Seats
  • Cracked Cylinder Wall
  • Gasket Issues
  • Damaged Timing Belt
  • Valve Problems
  • Worn Pistons or Piston Rings
  • Dropped Valve Seat
  • Broken Valve Spring
  • Holes in Piston
  • Bent Push Rod

A leak-down test or cranking compression test; can be used to see if the cylinder, is holding or pumping up normal pressure. As a rule, most engines should have, 140 to 160 lbs. of cranking compression; with no more than 10% difference, between any of the cylinders.

Causes Of, Low Compression, In All Cylinders:

  • Broken Timing Belt or Chain
  • Broken Camshaft
  • Worn Piston Rings
  • Bad Intake or Exhaust Valves
  • Flat Camshaft Lobes
  • Broken Piston Rings
  • Blown Head Gasket
  • Fuel Washed Cylinders
  • Carbon Deposits On Intake Valves/Valve Seats

So, if you have any of the above causes, the cylinder head will have to be removed. Another reason for removing the cylinder head is; if you find spark plugs that are, heavily fouled with oily deposits. Oil leaking past worn valve guides or seals, is usually the culprit. Installing new spark plugs will cure the symptom, but not the cause. Consequently, the permanent fix; is to replace the valve guides and install new, valve guide seals. However, not the fix, for low compression.

Fouled Spark Plug
Fouled Spark Plug

A spark plug that shows heavy whitish to brown deposits; may indicate a coolant leak either past the head gasket or through; a crack in the combustion chamber. This type of problem, will only get worse and may soon lead to even greater problems; if the leak is not fixed.

Also, a cylinder will not fire normally, if the valves are not opening and closing properly; due to a weak or broken valve spring or a rounded off cam lobe.


So, when compression gets below 90 pounds, the cylinder could misfire. You may need to do some, mechanical testing.

TIP: You can also do, a A running (dynamic) compression test.

Consequently, if you find that there’s low compression; you need to check all possible areas, where the problem may have come from. Including, the gasket, valves, pistons, and cylinder. As a result, any type of damage in these parts, can contribute to your problem.

Thank You !