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  1. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    If it feels worse in gear, could be the gearbox? How is it in neutral? I'd be surprised if it was misfiring but not reporting it. If I understood my research on these engines the crank position sensor is used to detect when the crank moves lined up with the timing of some cylinder firing. If...
  2. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    Yeah can't be too mad having all new parts in there! I have read multiple times that the odd misfire is normal and expected, they won't trigger any codes or CEL. I'm not sure how many exactly is considered "normal" though, I haven't found any actual numbers. I'm surprised you don't see any...
  3. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    Well turns out it was leaking from the spark plug the whole time. I always thought that the cylinder 8 plug got tight a little quicker than the others but I didn't want to force it and it did seem to thread in without too much trouble. In hindsight I think it wasn't even close to being properly...
  4. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    I re-seated the intake then later tightened up the intake bolts from the recommended 89 in lbs to 110 in lbs and it improved the cylinder wide misfires on cold start. Also got to check the driver side engine ground on the back of the engine and it was a bit loose. Still wasn't perfect on cold...
  5. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    Here's some live data recordings, misfires are on the top right, I would ignore fuel trims mostly because I have an unknown mix of 87, 91 and E85 in there which would affect those. Cold start until the cats warm up/revs drop, looks fine until the revs drop then seem some misfires across the...
  6. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    Copying from original post: I have a bluetooth ODB scanner with TorquePro, I'll see if I can do a screen recording of a cold start
  7. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    Injectors were from ACDelco from Summit: https://www.summitracing.com/parts/ADO-12742701 Everything so far has either been genuine GM parts or OEM manufacturer.
  8. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    Resistance on passenger side ground on back of engine has 0.1-0.2 ohm resistance and 0.1v voltage when running, access is tight but was able to get a 13mm back there and tighten it up a tiny bit, so seems good. Couldn't access the driver side coil/rail ground with the intake on, the one of the...
  9. Z

    5.3 misfire on cylinder 8 on throttle lift - SOLVED

    I'm chasing a weird misfire on my 2018 Tahoe with the L83/5.3 with 125k miles. It started off with a failed coilpack that I was able to diagnose from a misfire code, swapping coil packs and checking misfire counts on an ODB reader. The failed coil pack was producing hundreds/thousands of...

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