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.

A: Misfires are caused by lack of fuel or the ...

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

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: Rough idle, stalls when accelerating, engine shuts down while driving with no fault codes.

Hi there. The issue is the coolant thermostat temperature sensor. The sensor is malfunctioning causing the computer (ECM) to think that the engine is either too cold or too hot and causing the fuel mixture to be off. I recommend...

Q: Something locked up the wheels

Hello. I would recommend having your suspension and brakes checked. This will include removing the front wheels. With the wheel removed, it will be much easier to determine what the actual cause of the lockup is. The lockup may have...

Q: Random misfires

Hello. There are several possibilities that could explain why you are having this problem. One possibility is that you could have one or more faulty fuel injectors, or the fuel injector wiring is damaged. Another possibility is...

Related articles

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...
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 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...