Cylinder misfiring after spark plug replacement

886 Views | 7 Replies | Last: 2 yr ago by FC12
metrag06
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AG
Replaced the spark plugs on my 2019 CX-9 this afternoon - all seemed to go OK but very rough/smelly idle after replacement and flashing CEL. Code reader showed P0303. Tried to reseat all the coils but still getting misfire.

Engine will idle relatively smoothly now but lots of vibration lack of power when in reverse or drive. If I can't clear this up myself is it worth limping it to shop or should I have it towed?

Any suggestions?
Silvy
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AG
Make sure all them hoes well connected
Jack Cheese
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AG
Yep.

Next I'd check coils by swapping them and see if problem follows to a different cylinder.

Hopefully it's not this issue, though:

metrag06
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AG
Thanks - saw that vid but engine was fine prior to me mucking with the plugs and only at 47k miles. I'd put money on me not having something seated/tightened correctly.
Cromagnum
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AG
Lots of things to check.

Sparkplug not seated well.
Not connected well to coils (or a bad coil).
Not gapped correctly.
Bad sparkplug altogether.
Valve issue.
fixer
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Pull number three again.

Check for carbon tracking as sign of bad plug.

Many times I've had this same thing because the plugs had been dropped prior to me buying them.
metrag06
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AG
Pulled all four plugs and reseated them along with coils. I'd been working at a bit of an angle for last one due to some hoses so I pulled a few extra brackets loose to free up room.

Buttoned it back up and all seems OK now.
Jack Cheese
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AG
Good deal!
FC12
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I was going to say make sure you actually installed a plug into every cylinder…
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