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?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  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: My 03 blazer was driving fine and all of a sudden it sputters then quits and has not started since. The fuel pump hums....?

Hi there. To start a vehicle, the electrical system, composed of the battery and starter, turns the engine over. Once running, the engine requires a constant flow of gasoline and good spark to keep that fuel igniting. If gasoline is...

Q: Put key in ignition. Lights and everything come on for a second, then went off as I turned the key. Now no power, key stuck

Hi, thanks for writing in. This sounds like your battery cable connections are corroded or loose at the battery. Try to see if the battery connections are loose by wiggling them and see if power returns. If power returns, then...

Q: Q: Car won't start

As a general rule, car engines do not like cold weather and do not do operate as well in cold weather. When you start your car in the morning and turn the key to on, the coolant temperature sensor immediately...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
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...