Skip the auto shop - Our mechanics make house calls

Q: Random misfires

asked by on

rough misfire at idle,smell like fuel,when eccellerate car goes in limpmode and engine light stays on. already change four batteries because its draining after few km.car is not performing and revs stays low.

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

Engine misfires can be caused by many different problems, but there are a few suspects that occur more than others. 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

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: Car fob will not chirp when locking vehicle. I pressed lock button twice and panic button works fine. Please help!!!

Hello. Typically if the horn will no longer chirp when locking the vehicle it is because the control module has lost its programming or there is a problem with one of the door switches. If you are getting a door...

Q: car overheated.fixed cylinderhead gasket replaced sparks n wires cant get it running

Hello, thank you for writing in. When the engine overheats to a certain point, there is damage done to the engine that is irreversible. The biggest concern is that inside of the engine, the pistons can heat up to the...

Q: The car stalls occasionally as if the fuel is not been pumped

It sounds like you may have a fuel supply issue that corresponds to the load put on the motor when you turn the A/C on. This may be related to a faulty MAP sensor. The Manifold Absolute Pressure (MAP) sensor...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
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...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...