Misfire

2011 bought used about 10 months ago. Spark plugs were changed just before. Had the cylinder 8 misfire on. We have changed coil pack and fuel injector. Check engine light went off after each new part. What should i look at now?

You said had, is it still on? And how's the misfire. Best advice is to use a scanner that has a scope feature, so you can see spark pattern. It's possible that #8 spark plug is slightly fouled or messed up somehow due to the old coil or injector.

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Plug wire maybe since that’s the only thing you haven’t done? If you have a timing light you can check the wires easily.

Fuel injector was the last part changed. Light was off for 1-1/2 weeks then came back on. Thanks for answers to look at next.q

The problem is most likely one of the items you've changed. Perhaps that plug was skipped, as you weren't the one who did the work. As Moose said, maybe it's defective or not gapped properly? Maybe the "new" coil was a Chinese knock off that's no better than the old coil. Was the coil boot changed also? They can carbonize and misfire.

Of course there could be deeper problems that a knowledgeable compression check would help reveal. Could be a valve train or compression problem, but those would probably be more consistent. Could be a fouling plug from a bad oil ring.

If I were you, I'd switch the coil, injector, spring and boot with another cylinder. I'd pull the plug check its condition and gap. "Reading the plug condition" can tell you lots. Replace it with another or switch it with another cylinder. That would narrow down the problem.

Good luck. Let us know what you find.

Trainmaster hit upon something I hadn't thought of. Due to the severity of changing the back 2 plugs, some cheaters will ditch the 2 new plugs, and never say a thing about it. A friend that runs a Midas around the corner from me, said he had to fire his mechanic for just that reason. And #8 is way back there, drivers side. Without pulling it, or scoping it, you'll never know.

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We bought this from an uncle that started a small used car lot. So I know all plugs were changed. Also, update we did just change the #8 plug. So the next easy thing is to move the coils to another cylinder.

No.8 is the rearmost, hardest to reach, and last in order plug

If a plug in the set gets dropped, arrives defective, doesn't pass the gap test, mechanic gets lazy, whatever --- it is the most likely to be left as-is

Also, are you getting a Cylinder 8 specific misfire code each time, or do you just see rough idle and a CEL light that someone at some point read as a misfire on #8?

Sgt Darkness said:

Plug wire maybe since that’s the only thing you haven’t done? If you have a timing light you can check the wires easily.

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cdahlen said:

Fuel injector was the last part changed. Light was off for 1-1/2 weeks then came back on. Thanks for answers to look at next.q

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Fuel injector and the wire that connects it are 2 different things. You can borrow a noid light from Advance/Auto Zone for free and it only takes a moment, so you might as well check it if you haven't done so.

Adieu said:

No.8 is the rearmost, hardest to reach, and last in order plug

If a plug in the set gets dropped, arrives defective, doesn't pass the gap test, mechanic gets lazy, whatever --- it is the most likely to be left as-is

Also, are you getting a Cylinder 8 specific misfire code each time, or do you just see rough idle and a CEL light that someone at some point read as a misfire on #8?

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We have just changed #8 plug. Also the CEL code has always been the 8 mis-fire