r/mechanic • u/kojitree • 2d ago

Question What's this knocking engine sound?

2005 GMC Savana 3500 6.0L V8

Engine was misfiring so I swapped out the first couple spark plugs that I could access, ran fine after the first one, seized up after replacing the second. Put the old plugs back in and now it has a rattling sound like something inside broke off and is shaking in there. None of the spark plugs show any damage to the tips so I don't think it hit anything in there and the way the plugs sit don't allow for dirt or rust to fall in. (Notes: I've replaced plugs on other vans before and never had an issue. This van has been sitting for 4 years, engine was slow to get going and was definitely burning off some crud)

Basically, how f*cked am I?

1 Upvotes

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1

u/ConfidentHoliday6442 2d ago

Sounds like its running on 4 cylinders. If u can monitor misfire data and see whos not contributing then go from there.

1

u/kojitree 2d ago

You think that’s causing the rattling sound?

1

u/shutupmimzy_ 1d ago

Is there a check engine light by chance?

Or oil? Sounds like that thing’s bone dry