Car’s #8 cylinder is misfiring

There is a misfire in my car’s #8 cylinder. Even after changing the spark plugs and the ignition coil, I still have the misfire. When checking the compression in the cylinder, I found that it is good. Also, I checked to ensure that there is 12v going to the injector – that is fine, too. There is a code for the catalytic converter. Could the catalytic converter be causing the misfiring and if not, what do I look for next?
Experienced mechanics share their insights in answering this question :
It is possible that your oil ring could be faulty in the number eight cylinder. If the oil ring is faulty, this can allow oil to get past the piston into the combustion chamber and therefore causing it to get burned by the spark plug. This can cause a misfire because oil is much harder to burn than gasoline.

Extended burning of oil by a spark plug can eventually foul out the spark plug. If the oil ring is the only piston ring that is bad, this can still cause the compression readings to be within specification. I would recommend having your number eight cylinder checked by a professional to determine if there is evidence of oil in the combustion chamber. If there is evidence of oil, I would recommend having the oil ring replaced.

Have the vehicle inspected by a qualified mechanic, they will be able to diagnose the misfire firsthand and make the appropriate repairs.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Faulty ignition parts such as the spark plugs, ignition coils, spark plug boots and wires, or distributors. Faulty fuel system parts such as the fuel pressure regulator, fuel injectors, or the EGR valve. A large vacuum leak. A faulty powertrain control module.
Multiple misfires can be caused by many reasons from a faulty ignition system, fuel system, or internal engine failure. The most common reason for this to happen is faulty or worn-out spark plug coil packs, especially if it`s been a while since you had a tune-up.
The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.
An engine misfire is when one or more cylinders doesn`t produce power, and there are several possible causes, from a fouled spark plug to a clogged fuel injector or faulty oxygen sensor.
An engine misfire can be caused by bad spark plugs or imbalanced air/fuel mixture. Driving with a misfire isn`t safe and can damage your engine.
If left untreated, a cylinder misfire can lead to significant engine damage. Worse, if you experience a bad misfire while driving, it could result in an accident. This is why it`s important to treat engine misfires as soon as you detect them.
Yes, a bad catalytic converter is a likely cause of an engine to misfire. A blocked catalytic converter will typically overheat, which can cause damage to your car`s engine and result in a misfire.
Catalytic converter problems cause gas within your engine to heat up to the point that it actually ignites. This ignition is what causes the misfiring sensation – and that can destroy engine components. Anytime your vehicle misfires, you should have it checked out by a reputable service professional.
Use a spark plug socket to remove the plug to get a good look at it. The damage you see will help you determine the cause of the misfire. If the spark plug is just old, replacing it may solve the problem. Make sure to replace and properly gap new spark plugs.
A misfire will cause the engine to momentarily stumble, or lose rpms, and then regain its normal engine speed. The misfire will usually reappear, either under specific operating conditions or randomly. A misfire may occur when your engine is idling, causing a rough or uneven idle.
Regardless of the specific cause, mechanical misfires are the most serious in regards to how they need to be addressed because they aren`t merely going to go away in due time. Instead, they will likely fester and only worsen, leading to other engine damage if left untreated.
What to do? The best way to avoid an engine misfire condition is through following the scheduled maintenance in your manual. Keep your vehicle`s engine tuned according to factory specs. Plus, a yearly trouble-code scan by a well-equipped shop will uncover any potential problems before they become major faults.
Can a bad O2 sensor cause a P0300 code? Yes. As it is one of the most vital inputs to your car`s computer for fuel control, a sensor failure can result in an incorrect air/fuel ratio. In addition, it can lead to engine misfiring and set code P0300.
Even a dirty MAF sensor can cause a lean code and/or misfire to occur. The engine may be stalling because it isn`t getting enough throttle opening.
If an oxygen sensor or mass airflow sensor is failing, it could give incorrect data to your engine`s computer, causing the misfire.
Even a dirty MAF sensor can cause a lean code and/or misfire to occur. The engine may be stalling because it isn`t getting enough throttle opening.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

my truck was missing codes said cylinder 1&8 needed to be changed. did now 1,6&8 are missing.
ANSWER : Hello there, thank you for asking about your 2007 Ford F-150. The problem is most likely with the ignition coils misfiring. I would recommend having a technician from YourMechanic come to your home or office to inspect your misfiring problem and replace the ignition coils.

engine light-p303 cylinder 3 misfire, changed spark plugs,ingition coil and cylinder valves
ANSWER : Coils and plugs are usually the starting point for a misfire code, but some basic diagnostic work might save you some money. Sometimes I like to try swapping components from cylinder to cylinder to see if the misfire moves before buying expensive parts. There are a few other problems that could lead to a P0303, like ignition primary problems, vacuum leaks, or bad injectors, but those things are usually accompanied by other codes. It’s clear that you have a dead miss. When the ECU sees a consistent misfire, it shuts off the fuel to that cylinder to prevent damage to the catalyst. The the CEL will start blinking to warn you that you may be doing damage by continuing to drive. You’re at a point where you need to have a professional do some diagnostic work. by contacting Your Mechanic, you can have a technician come to your home or office to check out your misfiring VW and recommend a fix.

I put the wrong key in my car and a few weeks later my car just shut down and it will not start I believe it’s the computer but…
ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

What would cause 1st cylinder misfire, multiple misfire, all fuel injectors circuits open and o2 sensors heater circuit high on a 2008 Dodge Charger
ANSWER : Hello. It sounds like you may have the wrong parts installed on the car. Due to the fact that multiple people have worked on it you may have some parts that do not meet specifications. From what it sounds like to me though you either do not have an ECM in the vehicle with the correct programming or you have a connection issue. If all of the grounds are not clean and tight then that will cause this. if they are then the computer needs to be programmed to your vehicle at the dealer and that may take care of it.

Truck’s rpm fluctuates and shakes when idling, engline light on code reads: cylinder 8 misfire.
ANSWER : If spark and fuel have been eliminated as the cause, check for a vacuum leak. If there is one located near cylinder #8, it can be causing the misfire. If no vacuum leaks are detected, then a compression test is in order. There is a technical bulletin #PIP4138K from GM for this concern relating to a valve-train and/or camshaft issue. If you want to have this checked, a professional from YourMechanic can come to your car’s location to diagnose the rough idling to let you know what’s going on.

Replaced alternator on car 2 times each time shows it’s charging 14v let car run for a little bit then test drive and car voltage
ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.

Car’s #8 cylinder is misfiring
ANSWER : It is possible that your oil ring could be faulty in the number eight cylinder. If the oil ring is faulty, this can allow oil to get past the piston into the combustion chamber and therefore causing it to get burned by the spark plug. This can cause a misfire because oil is much harder to burn than gasoline.

Extended burning of oil by a spark plug can eventually foul out the spark plug. If the oil ring is the only piston ring that is bad, this can still cause the compression readings to be within specification. I would recommend having your number eight cylinder checked by a professional to determine if there is evidence of oil in the combustion chamber. If there is evidence of oil, I would recommend having the oil ring replaced.

Have the vehicle inspected by a qualified mechanic, they will be able to diagnose the misfire firsthand and make the appropriate repairs.

Water pump is leaking, do I need to replace the timing belt, too? The car also has a misfire on cylinder 3.
ANSWER : Hi there. If the engine has too many miles on a timing belt, then a timing belt is suggested for replacement. The misfire for cylinder 3 could be caused by a spark plug failure, fuel injector failure, or a problem with the cylinder.

First, check for the fuel injector. Start the engine and disconnect the harness to the fuel injector for cylinder 3. If the engine sounds different, then the fuel injector was working. If the engine has no difference in sound, then the injector was not working and needs to be checked.

Next, check the spark plug for a solid blue / orange spark. If the spark is weak, the plugs and wires need to be replaced as a set.

To check the cylinder if it is getting hot enough to burn fuel, put a compression tester on cylinder 3 and crank the engine over. There should be more than 130 psi.

If you need further assistance confirming the misfire diagnosis, then a certified technician from YourMechanic, can come to your car’s location for a second opinion on the car.