Skip the auto shop - Our mechanics make house calls

Q: My car has a misfire, poor acceleration, and poor fuel burn (all the coils are good)

asked by on

Bad missfire bad excelaration ruff idle and bad fuel economy. All the coils are good but have a code flashing then stop and start flashing again

My car has 217000 miles.
My car has an automatic transmission.

Hello and thanks for your question. Check the condition of the spark plugs to see if they are fouled out. If the spark plugs are in good shape, then unplug one injector at a time from the harness while the engine is running. Listen for the engine to run more rough than it already does. If there is no change when unplugging an injector harness to an injector, then that injector is not working.

If all of the injectors are working correctly, then you would need to perform a compression test to see if any of the rings are sealed inside the engine. The first puff on the gauge to the compression tester should be at least 1/2 of the max pressure produced. If the pressure is less than 1/2, then the rings are not sealing. If the pressure is 1/2 the max pressure on the first puff, then the rings are in good shape. Then you would need to perform a leak down test to determine if the valve train on the engine is not burned.

If you cannot determine the source of the misfire, then seek out a professional, preferably a YourMechanic certified technician who can assist you with your vehicle at your home or office.

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!
  • Home
  • Questions
  • My car has a misfire, poor acceleration, and poor fuel burn (all the coils are good)

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: Truck dies while driving - 2000 Dodge Dakota

Hello. You may have several issues at once contributing to the stalling. You will want to start by having the vehicle scanned for diagnostic troubleshooting codes. This can be done by a mechanic or at most local auto parts stores....

Q: Car won't accelerate and warning light flashing.

The flashing light you are seeing is most likely your Check Engine Light. When the Check Engine Light is solid, then this is letting you know that there is a problem with the emissions system in your vehicle. When...

Q: Stalling dying misfires

These issues may be related. The battery is basically just an electronic storage device which must be charged regularly by the alternator. A good battery that doesn't stay charged points to a failing alternator. A bad alternator can also cause...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...
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...