A misfire occurs when the engine fails to complete combustion within the cylinders. The vehicle still starts and still runs as this occurs, however if the misfire continues it reaches a severe problem, the misfires will cause the vehicle to “lurch” from the power train or the engine. This is often misdiagnosed as timing issues, when indeed it is a misfire. Sometimes the timing of the combustion is off though. There are several reasons for misfires. One of them is ignition timing. This requires an adjustment and then the misfires stop.
The misfire of the ignition occurs more than any other misfire. Face it, vehicles have parts that wear out as time goes by. If you look in your vehicle’s owner manual, you will see in the recommended routine services replacement of certain parts over the life of the vehicle. Spark plugs wear out as does the distributor cap and rotor, the ignition cable s and the ignition coil. When this occurs the ability to achieve a good spark diminishes, which causes a compromise within the combustion chambers. This normally wears out slowly over time. You may not even notice the initial misfires, but over time, you will experience complete interruption of the combustion process.
A lean misfire is the engine actually missing from having more air and too little fuel. You may notice this particular misfire during idle. You may notice it as the engine speeds up or slows down. This kind of misfire will mess with the fuel economy. Reasons for a lean misfire are a fuel pump failing, a stuck open ERG valve, a plugged fuel filter, a defect in the mass air flow sensor or a lead in the intake manifold gasket. When you first notice misfires on acceleration or slow down or during idle, bring the vehicle in to check these things.
The mechanical misfire comes from mechanical issues such as a leaking head gasket, broken rocker arms, worn piston rings, fuel infectors’ defects, leaking intake manifold gasket, worn out camshaft lobes, cylinder walls, and a timing belt slipping or worn. This misfire will thump from within the engine. A powertrain misfire feels like a jerky motion from the transmission and felt during shifting. Sometimes the jerking occurs when the gears shift at higher speeds too. This can occur when shifting too fast and it can be from a result of the brakes falling out of the round brake drums, or sticky shoes or pads. If these are felt, take the vehicle in for an inspection to correct the issues.