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

asked by on October 15, 2016

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.

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