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.

A: Hello and thanks for your question. Check t...

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

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Bad gas mileage

Hi there. The fuel mileage is never great in this car, but this is rather low. Most of the time if it is running fine and has recently dropped off it is because or a dirty air filter or a...

Q: Ac not blowing cold air what refrigerant do i use

R134A is the correct Freon to use. You'll need to have the A/C checked to see if you have a leak or another problem causing your power loss during acceleration. Another possibility is the AC compressor dragging against the belt...

Q: Unable to start after it rains or misfires until the engine heats up in high moisture conditions

Hey there. This misfire no-start in wet or damp weather is going to be caused by the ignition system of the engine. In order to isolate the cause you can remove the inside engine cover and then start the van....

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 to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...