4 Common Causes of Misfires
In our last article, we discussed what a misfire is and its common symptoms. So how can you determine what is causing your engine to misfire in the first place?
With so many engine parts involved, it is often difficult to determine the cause of a misfire. However, here are the most common causes to help you troubleshoot.
4 Most Common Causes of Cylinder Misfires
1) Ignition System Problems
Spark plug wear and gap misalignment are common problems because spark plug tips are delicate and spark plugs have a relatively short lifespan. If the spark plug gap is too large, the spark cannot always bridge the gap between the center and side electrodes. No spark means no power is being delivered during this cycle.
The ignition coil (and distributor) converts the relatively low voltage of the battery into the high voltage required by the spark plug. These components can wear out over time due to the heat generated during each ignition. If the insulation on the ignition coil wears out, all of the electricity may not be sent to the spark plug and ignition wire as it should be, but instead may take a different route. Because distributors are rotating mechanical parts installed on older cars, they are subject to wear. Sometimes, carbon, dirt, or water can get under the distributor cap and affect the distributor’s ability to transmit spark to the spark plug wires. Water buildup in the distributor cap can make your vehicle difficult to start or unable to start.
Ignition settings that are too early or too late can cause the spark to ignite at the wrong time, resulting in incomplete combustion and erratic engine operation. Use a pilot light gun to make sure the distributor is set correctly. Some older engines with electronic fuel injection (EFI) have sensors that can be adjusted in this manner (e.g. the cam angle sensor in older Mazda MX-5 Miatas). Vehicle-specific instructions can be found in your repair manual.
Spark plug wires wear out even faster than ignition coils and are a common cause of failure. Worn spark plug wires can cause intermittent, weak ignition, or no ignition at all. These can be tested with a pilot light gun or a multimeter with an inductive sensor. The pickups are placed around the ignition cable, and the device gives you a reading every time the cable fires. If your ignition timing light doesn’t come on, or your multimeter shows low or zero voltage, you know there’s a problem.
But don’t ignore the obvious: Make sure the ignition wires are securely connected to the ignition coil and spark plug. Disconnect each cable and check for corrosion. Corrosion can cause gaps between the coils, wires, and spark plugs, causing the engine to misfire on this cycle.
2) Fuel Problems
Having “bad gas” in the tank (wrong octane or old gas) can cause a misfire. Weak or dirty injectors can restrict fuel flow to the cylinders, resulting in an inaccurate air-fuel ratio. A clogged fuel filter can reduce fuel pressure and restrict fuel flow.
3) Electrical Problems
Problems can come from electrical problems external to the ignition system, such as: B. A defective air mass sensor. Other computer or wiring issues can block signals for things like how much fuel is injected, the timing of fuel injection and ignition, etc. Spark plug wires generate quite a lot of electromagnetic frequencies (this is actually how inductive pickup works).
4) Mechanical Issues
You should also check your engine for mechanical issues, since the system contains a lot of moving parts. Cracks can cause vacuum leaks or the timing belt or chain can slip, affecting the timing of valve opening and closing. Moving parts like pistons, connecting rods, and crankshaft bearings can break, and parts like valve seals, valve springs, gaskets, and cylinder heads can wear out. Even a blown spark plug can be a cause.
Valve problems are a common cause. Carbon buildup around the valve seat in the cylinder can prevent the valve seat from closing completely.