2015 Silverado cylinder 7 misfire

[Cleanchvy70]

In 2023 I had my lifters replace and now I'm having a code pop-up cylinder 7 misfire and engine light flashing with traction indicator. It's leaking a little oil and it's smoking (white) out the tailpipe. It's not making any noise just feel like it's not getting full power and running a little rough. We replaced 1. valve cover gasket 2. Check coils 3. Check sparkplug and it had oil on it 4. Check lifters. After that I was told it's possible that the valve stem seal is stuck. Took it to a shop and was told he changed vss and sparkplug but still same results. He's recommending a new motor wtf. It's a 2015 Silverado 5.3 with only 77k. I never missed a peep on the services. Any recommendations would be gladly appreciated. Thx in advance.

[Bikerjon]

15 minutes ago, Cleanchvy70 said:

In 2023 I had my lifters replace and now I'm having a code pop-up cylinder 7 misfire and engine light flashing with traction indicator. It's leaking a little oil and it's smoking (white) out the tailpipe. It's not making any noise just feel like it's not getting full power and running a little rough. We replaced 1. valve cover gasket 2. Check coils 3. Check sparkplug and it had oil on it 4. Check lifters. After that I was told it's possible that the valve stem seal is stuck. Took it to a shop and was told he changed vss and sparkplug but still same results. He's recommending a new motor wtf. It's a 2015 Silverado 5.3 with only 77k. I never missed a peep on the services. Any recommendations would be gladly appreciated. Thx in advance.

Compression test, Cylinder leak down test, then Power balance test to determine next steps. The smoke is worry some.

[Cleanchvy70]

Thx I'll look into that

[Gangly]

White smoke out the back is coolant being combusted, you most likely have a blown head gasket.

[Cleanchvy70]

I will ask later today when I speak with him

[PunchT37]

4 hours ago, Gangly said:

White smoke out the back is coolant being combusted, you most likely have a blown head gasket.

Or, a guy that didn`t know how to torque to yield. Maybe used old head bolts. Gasket might not be bad, yet.

[Cleanchvy70]

Heading there now to get answers thx

[Gangly]

5 hours ago, PunchT37 said:

Or, a guy that didn`t know how to torque to yield. Maybe used old head bolts. Gasket might not be bad, yet.

Either way, your pulling the head off the engine.

[PunchT37]

1 hour ago, Gangly said:

Either way, your pulling the head off the engine.

Not necessarily 

[Gangly]

2 hours ago, PunchT37 said:

Not necessarily 

Yes, necessarily. 

 

If you want to say you can replace the head bolts without removing the head, you are correct, but the steel bands of the head gasket are deformed if they are leaking, and deposits are being created between the steel layers.  LS/LT gaskets are MLS gaskets, and if you have coolant leaking into the combustion chamber through that head gasket, regardless of cause, then you now have deposits and moisture between the mating surfaces of the steel layers which are now warped due to improper clearances associated with improper torque specs and heat cycling.  That requires the head to be removed and the gasket replaced, otherwise you will have the same problem a few miles down the road, regardless of whether you removed old head bolts and installed new ones to proper torque.

 

If coolant is getting into the combustion chamber, the head needs to pulled, period.   

 

At best, all you will need to do is pull the head, clean the surfaces, replace the head gasket, and use new head bolts.  At worst, you have to mill the heads due to warpage from heat cycling under improper torque and heat cycles.  You can bootleg it if you want, but coolant in a combustion chamber is a ruined head gasket and that requires a head removal for effective long term use.

Edited October 23, 2025 by Gangly

[PunchT37]

My bad. MLS was not in my lame brain when I typed.

[Cleanchvy70]

Ok just left the shop and the lifter is stuck but don't know if it turned and did any damages to the cam shaft. Basically he can remove the lifter to see if it's cut up and if it's any damages to the cam. If it didn't turn he would replace lifter and I'll be on my way but if it turned and did damage he think it would be cheaper replacing the engine. My question is have you guys heard of a lifter turning? Before you guys go all in on me I hardly know anything about engines. I'm just looking for a little help. Thx

[PunchT37]

30 minutes ago, Cleanchvy70 said:

Ok just left the shop and the lifter is stuck but don't know if it turned and did any damages to the cam shaft. Basically he can remove the lifter to see if it's cut up and if it's any damages to the cam. If it didn't turn he would replace lifter and I'll be on my way but if it turned and did damage he think it would be cheaper replacing the engine. My question is have you guys heard of a lifter turning? Before you guys go all in on me I hardly know anything about engines. I'm just looking for a little help. Thx

They can turn in those plastic trays.

[Cleanchvy70]

That's what I was told thx

[newdude]

On 10/23/2025 at 5:10 PM, Cleanchvy70 said:

Ok just left the shop and the lifter is stuck but don't know if it turned and did any damages to the cam shaft. Basically he can remove the lifter to see if it's cut up and if it's any damages to the cam. If it didn't turn he would replace lifter and I'll be on my way but if it turned and did damage he think it would be cheaper replacing the engine. My question is have you guys heard of a lifter turning? Before you guys go all in on me I hardly know anything about engines. I'm just looking for a little help. Thx

 

 

Yes.  That's why GM wants them replaced too any time a lifter or all lifters are replaced.