PO300 random multiple misfires?

2007 CADILLAC ESCALADE ESV
150,000 MILES • AUTOMATIC
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FREERIDER78
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  • 23 POSTS
Truck is sluggish to accelerate then engine light flashes. Read codes and it's PO300 or specifically PO307. Coil swap with 5, code stays with 7. Live data running rpms very little to no change when disconnecting coil feeds on all cylinders, same with injector feed on 7. Removed spark plug wires on driver's bank and all coils giving strong spark. Was going to run injector pulse test before swapping an injector. Haven't checked plug but it seems like 7 is firing along with the rest. Any suggestions on next steps in diagnosis?
Jul 23, 2026 at 6:43 AM
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BENNETTLYLEEEEE
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The injector on cylinder 7 might be clogged or stuck. You could try swapping it with the one next to it to see if the misfire follows.
Jul 23, 2026 at 9:43 AM
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STRAILER
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I would check the spark plugs first, they might have never been changed at 150k. So the code is a p0307 correct? lets concentrate on that cylinder then. Go for the spark plug first, upload an image of it so I can see. Also, here is a guide to help as well

https://www.2carpros.com/articles/engine-misfires-or-runs-rough/

Let me know how it goes.
Jul 23, 2026 at 2:37 PM
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FREERIDER78
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Turns out the boot on #7 plug was loosely attached. The plug itself was worn to a .065 gap with the ground strap heavily worn. All the plugs were in the same condition. Replaced with AC Delco iridium and no more misfire. I think just pushing the boot on firmly would have fixed it but the plugs needed changing.
Jul 25, 2026 at 2:38 AM
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STRAILER
  • ✓ASE Certified Mechanic
  • 54,832 POSTS
  • ASE Certified Mechanic
Glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.
Jul 25, 2026 at 2:42 PM
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