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Q: Rough idle and SEL is flashing. I've replaced all 6 plugs and coil packs. The car still has a rough idle and no power.

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Rough idle. Sel flashing. Had a friend stop by with his scan tool and check. Was told 2,4,5,and 6 not firing. Replaced all 6 spark plugs as well as all 6 coil packs. Still have rough idle, no power and sel flashing again.

My car has 107000 miles.
My car has an automatic transmission.

A: Misfiring can be caused by lack of spark or...

Misfiring can be caused by lack of spark or lack of fuel. If the same cylinders are still showing codes for misfiring after replacing the coils, the problem can lie elsewhere. If it is the coils not firing, there can be an issue with the wiring harness from the engine control unit to the engine harness. Also, the engine control unit itself can be bad, not sending signals to fire the cylinders. Also, lack of fuel can cause misfiring. Dirty, clogged, or failed injectors can be at fault. Also, a wiring or engine control unit fault can prevent injectors from firing as well.

To avoid any unnecessary repairs, have a certified technician, like one from YourMechanic, come to your location and diagnose the engine misfiring to isolate the exact cause.

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