Q: Rough misfire at idle.

asked by on November 29, 2016

random misfire at idle with engine light on.(limpmode)

My car has 189000 miles.
My car has an automatic transmission.

Engine is misfiring Inspection $79.99 - $89.99 Get a Quote

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.

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

What others are asking

How do you change the unit of measurement in the message system?

Your car comes from the factory set to show English measurements. However, it can be changed to metric if you prefer. To change your units from English to metric, just: Cycle through the menu to find “units.” Press the...

Reverse lights not working

After replacement of both bulbs and the fuse, my next step would be the reverse light switch. Be sure to have your rear lights tested by a qualified technician before having it replaced, as it is not guaranteed to be...

hello Brandon my name is Marie,I have a 2005 pontiac bonniville gxp Im having crankshaft issues and oxygen sensors

Hi Marie: With regard to the code P1372 that was downloaded, there are many potential malfunctions that will cause P1372 to set in addition to the crankshaft position sensor itself being faulty. And, if the sensor itself is suspected as...

Car still shaking after replaced coils and spark plugs codes cleared still showing misfire in coil 3

The code P0353 on this after you only had misfire codes and you changed the coil and plugs on cylinder number 3. You should disconnect cylinder coil and check connector and pins in coil are not damaged and if they...

My steering wheel is locked.

Hi there. Sounds like the steering wheel lock solenoid is not working. To get to the solenoid or to remove the lock, you would need to remove the battery cables (both) and remove the horn with the airbag from the...

Stalling. 2005 Ford Mustang.

Hi there. Thanks for writing in about your 2005 Ford Mustang. This could potentially be a faulty fuel pressure sensor or possibly also a bad mass air flow sensor causing an imbalance in the air-fuel ratio. You should have the...

will a water pump fail without the temperature light showing?

When a water pump fails, it usually fails by seizing up. It is possible for a water pump to seize up without having any warning lights illuminated. Many times the water pump will make a noise because the bully is...

I just did a radiator flush on my car and now I'm loosing all my coolant out of my reservoir and my radiator what could be the iss

Normally, the cooling system pressure should be around 16 psi so if you have a reading of 13 psi, that would be considered low. If you are positive that you have a leak, I would recommend locating the leak and...

Starting problem: I turn the key on and everything on the dashboard comes on, all the lights work, but the truck wont start?

Hello. Try checking underneath the steering column where there should be two torque headed screws that connect the shift lever to the cable. These tend to get loose or even fall out sometimes. There are also bushings in the shifter...

Related articles

The Check Engine Light Demystified
Your car Check Engine Light can mean many things. The Check Engine Light comes on when there's an electrical or mechanical problem with your car.
The Best Used Cars to Buy If You're a Dog Breeder or Trainer
These These days, dogs are more and more likely to travel with people than ever before. After all, what dog doesn’t ride in a car? As a breeder and trainer though, you’re probably more likely to carry along dogs than...
The Best Used Cars to Buy If You're an Undercover Cop
If If you're an undercover cop, when you choose a used vehicle, your main purpose is to look like anything but a cop. That means, of course, that an unmarked Crown Victoria is probably not the wisest choice. We’ve...