misfire and electrical issues with 08 silverado

[R33V3S]

I bought a used 2008 silverado 1500 4x4 extended cab and have been fixing all the issues it has. I just can't seem to track down why it has a random misfire and some of the electrical issues. I have replace spark plugs, plug wires, ignition coil packs, mass airflow sensor, cleaned the throttle body, replaced the 02 sensors, had the injectors tested. the other issue is that it only displays the trans temp, mileage, and trip mileage. If anyone has an idea of anything else to try I need the help

Edited September 14, 2021 by R33V3S

[Jsdirt]

Most random misfires that aren't ignition related on this vehicle are either failed lifters, cam, or other valve train components, or intake manifold air leaks.

 

Get a scan tool on there and watch live data. When cold but in closed loop, watch the fuel trims or o2 sensors - if everything goes real lean (positive fuel trims),  give it a little throttle - if they suddenly get normal, that's usually a dead ringer for an intake manifold leak. Confirm that with a spray bottle full of water, and mist the gasket surface between the manifold and head. You'll either see immediate changes in fuel trims & idle quality, or you'll hear it getting sucked in through the leak.

 

These things are notorious, especially the 5.3, for failing lifters, so that needs to be ruled out as well. If this ends up the case, do LOTS and LOTS of RESEARCH - this engine will burn you bad with all it's little pitfalls. For instance, if you attempt to reuse the VLOM, the misfires will remain after you're over 20 hours of labor deep. There's a bunch of other little things, so READ, READ, READ. 

[R33V3S]

15 minutes ago, Jsdirt said:

Most random misfires that aren't ignition related on this vehicle are either failed lifters, cam, or other valve train components, or intake manifold air leaks.

 

Get a scan tool on there and watch live data. When cold but in closed loop, watch the fuel trims or o2 sensors - if everything goes real lean (positive fuel trims),  give it a little throttle - if they suddenly get normal, that's usually a dead ringer for an intake manifold leak. Confirm that with a spray bottle full of water, and mist the gasket surface between the manifold and head. You'll either see immediate changes in fuel trims & idle quality, or you'll hear it getting sucked in through the leak.

 

These things are notorious, especially the 5.3, for failing lifters, so that needs to be ruled out as well. If this ends up the case, do LOTS and LOTS of RESEARCH - this engine will burn you bad with all it's little pitfalls. For instance, if you attempt to reuse the VLOM, the misfires will remain after you're over 20 hours of labor deep. There's a bunch of other little things, so READ, READ, READ. 

I'm learning that it will, that's why I've tried to cover my basis with all the simple maintenance that needed to be done anyway. It might just be time to hand it over to a mechanic and let them sort all the issues out, while I was looking tonight I found the fuse box wasn't grounded and it had several blown fuses. Any chance you would know why I can sometimes see more settings on my dash cluster than other times, it's like the settings disappear.

[Jsdirt]

Sounds like a cluster issue. I'm not sure where the magic box lives that handles all of that - more than likely it's just a tiny chip on the cluster board. Could be failed or failing buttons as well. I have zero experience with that issue. These trucks are among the worst GM has ever built as far as build-quality goes. They seem to get worse with every generation, so, things COULD be worse, lol.

 

I could write an entire page of stuff that's gone wrong with mine. 2 of the latest were the rear differential after it shed all the tips of the spider gear teeth off for no good reason at 97k miles, and the transmission that burned up the 3 / 4 clutch pack without warning at 103k miles. One minute it was shifting fine, the next, a big flare in 2nd gear, then neutral afterward. Fluid was as red as the day I flushed it 50k miles prior. I replaced the rear diff with an OX air locker, and the transmission with a PerformaBuilt heavy hauler with 5-pinion planets. Now I can somewhat trust the thing, but the engine and transfer case are still left to fail. I'm at 113k now, so that could be any day now.

 

I paid so much for this crapbox that I have to keep it going for the next 30 years at a minimum. Got my work cut out for me, that's for sure!