My car has 160000 miles.
My car has an automatic transmission.
With the recent repairs made, chances are your issue is related to the fuel-system or a stubborn sensor that's on its way out. When was the last time you changed your fuel filter? The fuel injectors can also cause misfiring issues. If they are dirty or clogged a cylinder will not receive the amount of fuel it needs.
You should also have the vehicle scanned for any codes. Faulty sensors can trigger diagnostic trouble codes for this exact reason. Components like the EGR valve can also fail and cause misfiring. It will also help if the diagnostic codes will tell you which cylinder is misfiring. You can always check repairs recently made to those components. It possible to over-tighten a spark plug, which would leave unburned fuel and a smell of gas. To have this all scoped out more thoroughly, have a certified professional from YourMechanic diagnose the misfiring issue in person so that this problem can be resolved.
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