Skip the auto shop - Our mechanics make house calls

Q: Spark plug misfire and car not starting

asked by on

My check engine light came on and it say i have a misfire in my number 4 spark plug. Now sometimes my car wont start i have to keep trying and then eventually it will catch and start. Could that be from the spark plug?? Keep in mind a diagnostics shows my alternator and battery is good also i just got a knew starter.. Pleasee help i put so much in this car im tired of having issues!!.
My car has an automatic transmission.

A: Generally, misfires are caused by either a ...

Generally, misfires are caused by either a spark or fuel issue or in cases, a combination of both. Spark related problems generally will result from things like ignition coils, crankshaft position sensor, spark plugs, spark plug wires or ignition modules not working properly. When the misfire results from a fuel related issue, this is commonly related to a lean fuel condition (lack of sufficient fuel supply to the motor). Fuel related misfires can be caused by many different things such as low fuel pressure, faulty or dirty fuel injectors, a faulty O2 sensor, a dirty or failing mass air flow sensor, a faulty or dirty idle air control valve or a vacuum or intake leak. When the fuel supplied to the combustion chamber is insufficient, this results in an ignition (spark) that is igniting a less than balanced load of fuel and air. This results in a misfire or an explosion in the cylinder that is much less powerful than the other cylinders. This creates a loss of power that resonates throughout the motor additionally causing other problems with ignition and fuel timing. Due to the number of different things that may cause an engine misfire, the quickest and easiest way to diagnose this type of problem is to hook the vehicle up to a scanning tool which will download any potential fault codes that may have registered in the vehicle's computer as a result of the poor running condition. I would recommend having an expert from YourMechanic come to your location to diagnose your misfiring problem.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Vehicle misfiring and I don't know why

Hi there. The ignition system on this engine includes the distributor, cap and rotor. The distributor is a common issue on this engine due to failure of the sensor inside of it. The sensor will cause an erratic RPM signal...

Q: Grumbling sound while breaking at the stop light, brake pedal shakes

You are exactly right. It is your anti-lock braking system that is engaging when you hear that buzzing sound. A number of things could cause the anti-lock braking system to engage when it shouldn't. Some of these things would include:...

Q: AC only blows hot air

Hello. We will be happy to assist! To diagnose an AC concern, I first suggest checking the freon levels as it is the most vital component to the health of the AC system. Then, a technician should attempt directly switching...

Related articles

How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...