Truck shaking/odd idle after changing plugs and wires

[midnightsilvy]

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]

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]

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]

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. 

[Frankielozano214]

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 

[midnightsilvy]

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.

[Snowcamo]

What plugs did you use?  E3?

[midnightsilvy]

Used AcDelco plugs, same part number as in my manual, 41-114 I believe it is

[Snowcamo]

They may need to be gapped properly. Any chance one got bumped while putting it in?

[midnightsilvy]

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

[Snowcamo]

Hopefully it is a simple misfire.  It has to be a simple fix

[midnightsilvy]

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]

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.

[midnightsilvy]

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]

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 December 28, 2024 by txab