Q&A for How to Fix an Engine Misfire

The most common culprit for an engine misfire is lack of spark—usually because the spark plug needs to be replaced. Another common reason would be the spark plug wire, which delivers the spark from the ignition coil to the spark plug, and then the coil itself, which generates the electricity that's sent through the wire into the spark plug. Those are the three most common causes. More extensively, there may be combustion issues inside the engine.

This is likely due to weak rings. You can use a leak-down tester to check this theory. Hook up the tester with the piston at the top, dead center and listen at the oil fill, coolant reservoir, tailpipes and exhaust. If you hear air coming from the oil fill, then the rings are not sealing properly. Full disassembly would be needed to determine the exact cause and extent of damage.

It depends on how old your car is and what the actual issue is that's causing your engine to misfire. For instance, if you have a problem with one of your ignition coils, it could cost you around $300 USD for a mechanic to fix it. But if you have a newer model vehicle, it could cost you $400 USD to fix the same issue because of the price of the parts that need to be replaced. Usually, fixing a misfire is a pretty straightforward repair. However, there could be a deeper issue causing it, so it's always a good idea to have a professional mechanic look under your hood.

While you may be able to keep driving for a while if your car has a misfire, in the end, it's really not a good idea. Usually, a misfire is caused by a problem with one of the cylinders, and if you keep driving around with it, it could cause much more serious and irreversible damage to your engine. Sometimes, a simple fix, such as replacing a spark plug, can solve the issue, so if your car is misfiring, don't ignore the problem it it will only get worse (and more expensive).

Technically, no. Having a low level of oil in your vehicle won't directly cause your engine to misfire. But, if you do have a misfire and you notice that your low oil pressure light came on, it could be because your engine is running on low oil, which can cause other mechanical issues. Some of these potential issues could cause multiple malfunctions, including a potential misfire. So while having low oil doesn't make your engine misfire, if you don't maintain and take care of your engine by making sure it has enough oil, it could malfunction and wear down, which could eventually lead to issues like misfires.

You may be having a problem with one of your coils. Spark plugs ignite the air and fuel mixture using current transmitted from the coil pack, so a faulty one can result in a misfire. Many vehicles will provide a specific error code if a coil goes bad, but you can test a coil by disconnecting the spark plug wires and connecting an Ohmmeter (multimeter) to the top two pins to see if one of your coils is causing the problem.

A noisy engine can signal that a cylinder misfire is occurring. To better understand the problem, try plugging an OBDII code scanner into the port beneath the dashboard on the driver’s side. The scanner will give you an error specific to a cylinder misfiring or a generic misfire error across all cylinders. If you don't have access to a scanner, you can usually take your car to a mechanic shop, and they'll run the test for free.

A spark plug that looks black or carbon fouled at the end means the engine was running rich (too much fuel). A plug wet with gasoline or oil means the fuel regulator may have failed or there are serious internal issues inside the engine block. If the plug looks fine, check the gap between the metal sticking out of the end of the plug and the base. Compare that gap to the specified gap in the vehicle’s repair manual. If the gap is too big, it may be preventing the air/fuel mixture from firing.