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Truck shaking/odd idle after changing plugs and wires

midnightsilvy

By midnightsilvy
in Troubleshooting & Recalls

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midnightsilvy Enthusiast

midnightsilvy

Posted
Posted

Hi all, so recently changed spark plugs, wires and coils on my 2018 5.3 Silverado. Changed all but cylinder 8 (dumb, I know) given it's quite hard to reach and we were already hours in by then. Truck drove totally normal first day or two after, but now it's been off.

 

Most noticeably starts shaking under light throttle at cruising speeds, as well as rpm drops and lighter shake at idle (any gear). Other than this drives normally as it should

 

Thinking it either has something to do with new plug and wires on all but cylinder 8, throwing off timing and misfiring? Or a bad wire connection. I don't believe it's a bad part, otherwise problem should have persisted from the start.

 

Just wanted some insight from others before spending more or taking it somewhere for diagnosis. Will follow up later if what I listed above fixes the problem.

Snowcamo Senior Enthusiast

Snowcamo

Posted
Posted

The boot on the sparkplug needs to be twisted to let out the trapped air. If not it pushes the boot back. Hopefully it's just a connection issue. 

Frankielozano214 Senior Enthusiast

Frankielozano214

Posted
Posted
3 hours ago, Snowcamo said:

The boot on the sparkplug needs to be twisted to let out the trapped air. If not it pushes the boot back. Hopefully it's just a connection issue. 

Might have to check mine, have the same issue with my Escalade smh.

Snowcamo Senior Enthusiast

Snowcamo

Posted
Posted
46 minutes ago, Frankielozano214 said:

Might have to check mine, have the same issue with my Escalade smh.

Possibly so, twist back and forth a bit while pushing the boot on. 

 

I had it happen and I did not notice till I saw a few boots were furthure back on the plug then others. 

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Frankielozano214 Senior Enthusiast

Frankielozano214

Posted
Posted
12 minutes ago, Snowcamo said:

Possibly so, twist back and forth a bit while pushing the boot on. 

 

I had it happen and I did not notice till I saw a few boots were furthure back on the plug then others. 

Mine at idle has a light shake u can feel it when im at a red light or parked, drives good beside that minor issue. I’ll check them tomorrow 

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midnightsilvy Enthusiast

midnightsilvy

Posted
  • Author
Posted

Checked all the plugs and wires today. Everything feels good and solid.

 

Another thing I noticed is constant backfiring at the high end, like 4500+ rpm or so, maybe higher. And still doing the other things I had mentioned before, though the shaking under light throttle (seems) to be less

 

I'm pretty much at a loss at this point, I don't know what else could be the problem. Any help would be greatly appreciated.

midnightsilvy Enthusiast

midnightsilvy

Posted
  • Author
Posted

There was one we regapped that was pretty badly off, rest of them were all pretty much the same but no telling for sure without pulling them back out to check. 

 

Likely just going to take it to dealer and have them pull them to check, we spent so much time on it I'm not pulling them myself again

 

Engine light randomly came on today as well so whatever code it reads might point in the right direction

midnightsilvy Enthusiast

midnightsilvy

Posted
  • Author
Posted

Yea... hopefully. It really seems like something small but we'll pull whatever code it's reading and go from there. 

 

I'll update again later on when I have more info.

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted

This should have been a fairly simple job, why was there so much difficulty?

 

I say it often: new parts does not equal good parts.

 

Also, changing a plug, wire and coil will not change the timing. Messing one of them up can cause a miss fire though.

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midnightsilvy Enthusiast

midnightsilvy

Posted
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Posted

A simple job, yes. As you said, new doesn't equal good, and clearly the truck doesn't like something

 

I'm just some college kid so I don't know a whole lot yet. Just trying to figure out what that something is she doesn't like.

txab Senior Enthusiast

txab

Posted
Posted (edited)

Why did you feel the need to change coils? Coils can last a good while. I'd put the old coils on and see what happens. Yo may have poor connection at the coil coming from the wiring harness. Where did you get the plugs? They could be counterfeit if purchased from Amazon and similar. What brand plug wires? Maybe they are crappy. Lots of things to look at.

maybe you knocked something loose. Maybe a wire somewhere got pulled

Edited by txab
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