Q: Misfire on cylinder 8

asked by on September 23, 2016

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?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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

Just rebuilt the transmission and after picking up the car it's making a vibration . 2006 Acura TL

Hi there - a key question in resolving a vibration issue is "Is the vibration related to vehicle speed, or engine speed?". If the vibration comes from the engine, even if the car is not moving, there could be a...

Pick up shuts off when slowing to half stop then accelerating

Hi UK. Thanks for submitting your question today. Usually good fuel economy and mysterious engine shutting off issues is not related to a single component failure. If the fuel efficiency is good and the Frontier runs good (except for when...

Do i have to use synthetic oil in my bmw

The manufacturer recommends 5w40 or 5w30 full synthetic oil only for your car's engine. I would recommend only using full synthetic oils.

Related articles

What Does the DSG Transmission Too Hot Light Mean?
When the DSG transmission too hot light is on, your engine needs to shut off and cool down before serious damage occurs.
Ten Sports Cars That Double as Good Daily Drivers
The best daily driver is a car that's reliable, usable, and still fun to drive. Popular daily sports cars include the BMW M3, Subaru WRX, and VW GTI.
How to Get BMW Dealership Certified
BMW car dealerships offer automotive technician jobs to mechanics who are certified through the Universal Technical Institute (UTI) program.