2000 Yukon Denali misfiring on cylinders 1 and 7.

Discussion in 'Engine Performance + Maintenance' started by Dd1994, Apr 10, 2019.

  1. Dd1994

    Dd1994 Newbie

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    Thanks,
     
  2. Dd1994

    Dd1994 Newbie

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    Just wanted to add that the misfires stop when you rev the engine. Idk if that's helpful.
     
  3. Dd1994

    Dd1994 Newbie

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    Dry compression test done while engine was hot was also normal. (Cylinder 1 and 7 were slightly higher than 3 and 5 but within normal range), and were the exact same as cylinder 2 and 8.
     
  4. inscarguy

    inscarguy OBS Enthusiast

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    Have you checked the basics? Cap, rotor, wires. Kinda would explain that the skipping goes away as it revs up. Also clean MAF due to it sitting. Can't hurt to throw some Marvel mystery oil in the oil.
     
  5. Dd1994

    Dd1994 Newbie

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    Already put marvel mystery oil when I changed the oil, I haven't checked the cap and rotor but I will when I do the manifold. But when I put the spark tester on the plug for cylinder 1 which is one of the ones that's misfiring it seemed to be sparking fairly regularly. Also of note is that bank 1 is running normally or slightly lean around 5% and bank 2 is running rich at around -10%.
     
  6. Dd1994

    Dd1994 Newbie

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    also it appears the wires were changed recently before the car was put away, as they are aftermarket and look less old than the rest of the engine. I have a video of the car running if that is in any way helpful.
     
  7. inscarguy

    inscarguy OBS Enthusiast

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    Another thing you may want to check is the wiring. If it has sat for that long animals could have chewed the wiring and there is a problem somewhere.
     
  8. mars2878

    mars2878 I'm Awesome

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    after replacing my plugs, wires, cap & rotor, my rough idle didn't go away. it was suggested that my wires weren't laced correctly. 2 of my wires didn't match the diagram, so I relaced those 2 & no more rough idle. while it didn't solve my misfire, it sure does run smoother.

    plug wires, lace - vortec 5.7L.png plug wires, lace - vortec 5.7L.2.png
     
  9. Dd1994

    Dd1994 Newbie

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    I will check the wire routing out. Currently I'm just waiting on the spider to arrive to do the manifold. I think I'll be doing it this coming weekend.
     

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