Skip the auto shop - Our mechanics make house calls

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.

asked by on

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.

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.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. 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.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Every time I brake I hear a noise and it gets worse when the car is coming to a stop.

Any noises coming from brakes or changes in brake pedal feel, warrant an inspection right away for safety. You just don't know until an experienced mechanic has inspected your brakes. Brakes should be checked about every 15,000 miles or once...

Q: Truck not starting - 2002 Chevy Trailblazer

Hello there. There are many faults that can cause your 2002 Chevrolet Trailblazer to crank but not start. The most common causes of a no start condition is the battery, starter, battery cables, ignition switch, fuel pump, wiring harness fault,...

Q: Pulsating Lights

The battery and charging system is most likely the malfunction. If the battery is shorting out internally it would cause the alternator to not charge. There is a technical bulletin about not using re-manufactured alternators on these cars since they...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...