Skip the auto shop - Our mechanics make house calls

Q: Rough idle and engine misfire

asked by on

Ford focus mk2.Car have a rough idle and misfire,smell like raw fuel, causing limpmode when driving(malfunction transmission).Car have no power when accelerate. Took car for diagnogstic with no success.Service transmission,still have the same problem.

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

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 misfires, with a P0306 code 2001 Dodge Intrepid 2.7L

Hello - I note that you do not mention replacing the plug wires and plug boots. If these components were saturated with oil by the leaking valve cover gasket, they may still be shorting out, even with new plugs and...

Q: Squaling noise

In most cases, the squealing noise from under the hood is caused by worn out or damaged belts, including the serpentine belt, AC belt or power steering drive belt. If your 2005 Altima has more than 50,000 miles, it may...

Q: Not getting fuel to transfer to lines after changing pump and filter.

Hello, thank you for writing in. The first thing you want to do is make sure you are getting power to the fuel pump. Turn the key to the "On" position and listen for the pump to prime. You should...

Related articles

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.