Motor Issue

[Smithkennard]

Hello, can anyone help me out? I have a 2015 Yukon Denali with a 6.2 motor I recently had my motor “rebuilt” but the day I picked it up it’s been cutting off since I got it back, no check engine lights, no warning. Sometimes it restart with no problem, sometimes it start with a drag and then other times it doesn’t start til it sits for a while. Have anybody experienced this issue.

 

[Big Mama]

By rebuilt do you mean the cam and lifters with DOD/AFM delete? When it hard starts or fails to start is it turning over?

 

[diggler9366]

So i have a 2016 GMC Yukon XL Denali with the 6.2 l86 motor. started running extremely rough. had to get towed home. hooked up the scanner and found a p106 and a p300 code. so i pulled off the MAP sensor and checked the senor with the OHM meter and then with a vacuum gage. The sensor is with in spec. So i tired to start and it ran but rough. i smelled a lot of sulfur smell and found that the CAT's were really hot for the short time it ran. so i replaced the CAT's and used new clamps and gaskets. It ran a little better but after the thing warmed up it stalled out and wont start again. took the intake duct and pvc lines off and looked inside the plentium. found oil in the intake manifold. I don't know anything about the 6.2 as it is the first vehicle i have owned and worked on. not sure where else to check. or what else to do to fix this problem. any help will be appreciated

 

[Smithkennard]

By rebuilt do you mean the cam and lifters with DOD/AFM delete? When it hard starts or fails to start is it turning over?

Sorry for the late response. No delete but everything was rebuilt with OEM parts. When I try to start it, it’s spinning but not turn over. I went back to the yesterday where it was serviced now they telling me a msd wiring harness had to be ordered but it wasn’t doing it before the rebuild.

 

[Fless]

I'm not sure what you mean by "...it's spinning but not turn over."

Does that mean that the engine cranks over but doesn't start? (crank-no-start)
Or that the starter seems to spin but the engine doesn't crank? (engine doesn't turn over -- no crank)