Skip the auto shop - Our mechanics make house calls

Q: Misfire on cylinder 8

asked by on

I use premium gas. When I start my vehicle, it is fine, but after about 5 minutes of driving it is just not running right, it goes from smooth to rough. The misfire diagnostic came from a code reader a friend of mine owns. I had a complete oil change, a full service done only a couple of days ago, so all is good on that front. Puzzled.

My car has 144000 miles.
My car has an automatic transmission.

Misfires are caused by lack of fuel or the ignition system isn’t providing the needed spark. At least these are the most common single cylinder failures. It is possible, all be it remotely, that you have a compression problem, but this would reveal itself when cold as well. Compression problems don’t come and go.

The good news is you know which cylinder the problem is at. My first question to you is, how many miles ago were your spark plugs replaced? Most cars don’t go beyond 60,000 miles. Some do, but this only means you will experience a failure with a spark plug instead of replacing them before they fail. Without knowing what was done with your full service, this very’s quite a bit based on many factors, I cannot say for certain what to do next. If your ignition system was serviced along with your full service, I would take the car back to who did the work. This will likely fall under a warranty issue with them.

Injectors can fail and clog. If you have an injector problem in cylinder number eight, it can be cleaned with the appropriate injection cleaning machine. The machines work much better than dumping something into the fuel tank. The injector is an electric component that under goes much stress. It may have electrically failed.

A thorough diagnostic test should be performed by a qualified technician. I recommend the following service from YourMechanic; engine is misfiring inspection which can be performed by an expert at your home or office.

Good luck!

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・Fair and transparent pricing

Get a quote

What others are asking

Q: My van was missing and rough idling then I turned it off one day and the next day it starts then dies and some times it won't start

Hello, thanks for writing in about your 2001 Dodge Caravan. For certain, given your mileage and codes for these 2 components, replacing these 2 sensors is the minimum. Cleaning the idle air control valve, throttle body, and PCV valve should...

Q: Car is sputtering while in drive or reverse

This can be caused by a variety of reasons however a common reason for many engines to struggle may be a faulty throttle position sensor or mass air flow sensor. The throttle position sensor is a sensor that monitors the...

Q: Engine problems.

Hello. From what you describe it would appear that your vehicle is experiencing some serious performance and maybe even mechanical issues. If you believe the noise is coming from your turbo area it may be possible that the turbo is...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.