In Summary
  • This will affect combustion and result into a misfire. Observe if your engine loses oil. You can ask a good mechanic for a compression test to observe if your engine meets the specified values.
  • This will signal if you need to replace the piston rings. My first hunch is get a computer diagnosis and inspect the ignition coils. Let us know how it goes.

Hi Paul, I drive a VW Golf 4 which misfires and makes a strange noise as I accelerate. My service bay attendant replaced the spark plugs but the engine still performs the same way. My fuel consumption is high. What could be the problem? Joseph Kahuma

Hello Joseph, that sort of misfire can be caused by one of these three issues. Faulty ignition coils, damaged fuel injectors or poor engine compression.

The ignition coil is an induction coil on a modern electronic fuel injection engine which converts battery low voltage into high voltage enough to ignite a spark plug.

When the ignition coil is aged or damaged the voltage delivered is weak or nonexistent. This affects spark plug performance regardless of whether they are new. Faulty fuel injectors will not deliver the fuel at the required pressure or will flood the engine. Either way the performance of the spark plugs will be affected.

In such a case you will experience or notice a lot of unburnt fuel in the exhaust. Poor compression can be caused by damaged piston rings which allow the fuel air mixture to escape from the piston bore during the compression stroke.

This will affect combustion and result into a misfire. Observe if your engine loses oil. You can ask a good mechanic for a compression test to observe if your engine meets the specified values.

This will signal if you need to replace the piston rings. My first hunch is get a computer diagnosis and inspect the ignition coils. Let us know how it goes.