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Q: Car sputters and has weak power after new spark plugs and ignition coil were recently replaced

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Several months back my car was experiencing sputtering, weak acceleration (in the lower gears) and poor power and undesirable fuel economy. So I replaced the spark plugs and this helped for a few months and then recently the issue cropped again so I replaced the ignition coil and this helped marginally, the sputtering isn't as bad but there's still a lack of power and good normal acceleration. I'm curious if there's another issue outside of the ignition and spark plug system that could be causing this symptom. Thanks!

My car has 200000 miles.
My car has a manual transmission.

A: There are actually several possible causes ...

There are actually several possible causes for the engine to sputter. It is possible for there to be a vacuum leak, a faulty oxygen sensor, a catalytic converter that is starting to show signs of failure, or even a possible problem in the fuel system. It will be necessary to do some further diagnostics to determine which system is causing the problem, and then figure out which part in that system is the root cause. For example, if it is found that there is low fuel pressure in the system, it will then be necessary to figure out if there is a weak fuel pump, clogged fuel filter, or something going on with an injector. If the problem appears to be with the ignition, there could be a problem with a spark plug, ignition coil, ignition control module, or a fault in the wiring. I understand you said that the plugs and coil had been replaced, but it is possible that one of them have failed again, since the problem is recurring. If this is something you could use a hand in identifying, I would suggest consulting a certified mechanic, like those available at YourMechanic.com.

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