Skip the auto shop - Our mechanics make house calls

Q: Rough misfire at idle.

asked by on

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

My car has 189000 miles.
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

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: Missing throughout driving range.

The 2.3 L engine is a very dependable engine that has been around for a long time. If the misfire code is always for cylinder number 3 then you will have to look at the possible problems with that cylinder....

Q: My car has a rough idle, cuts off sometimes at a complete stop, and hesitates during acceleration

Hi - this could be a problem with the idle control valve, either dirty or failing. Leaking fuel injectors, clogged air filter, or low fuel pressure might also cause the symptoms you have noticed. I would recommend having a...

Q: My 98 Dodge neon fuel pump fuse keeps blowing?

If the fuel pump fuse keeps blowing then the most common cause of this the fuel pump in the tank is drawing too many amps and blows the fuse after it overheats. Replace the intank fuel pump and the filter....

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.