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Q: Car running very rough

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My car is running very rough. I have tried Seafoam in the tank, but it hasn't helped. I might need new spark plugs.

A rough idle can be caused by many things. Injector problems, worn ignition components like spark plugs and wires, or vacuum leaks are all examples of things that can cause symptoms similar to what you are describing. Products like Seafoam are not really meant as a repair, but are more like a maintenance. Here is an example of what I mean: If you have a cavity, brushing your teeth more often wont fix the cavity. It needs to be filled, then you can brush your teeth more often to prevent it from happening again. This is what happens with products such as the one you used. If used as part of a maintenance to prevent they work fine, but they are not meant to correct already occurring conditions. I would suggest getting a mechanic, such as one from YourMechanic, to take a look your vehicle to determine the cause of the rough idle. Running a car with a misfire can damage the catalytic converters making the repair more expensive in the long run.

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