GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hi there, I am Cam. The misfire on 4 & 6 is undoubtedly lifters based on what you have done so far. The key though is when running, watching those rocker arms, they won't have play or be loose, rather you would see them simply not move as the rest do. Did you check with the valve cover off while running?
Compression checks the piston and valve sealing. If you had the intake valve opening and not the exhaust, you would have normal compression. Yes, with it running you would see the rocker twitch but not move the same as the rest of them.
The compression test checks to movement and sealing of the cylinder as well as the valves, but there's a flaw in that logic. If the intake valve opens but the exhaust valves the thought, you will get perfect compression. With the valve cover off, you will see that valve rocker switch, but you will notice the movement is not The same as the rest.
The odds of the camshaft being bad are very slim, as well as the valve oil manifold. Usually only lifters as well as the filter screen on the oil manifold need to be replaced. You would be wise to replace all of me active cylinder deactivation lifters on that side of the engine During the repair.
The screen should be under the sensor in the manifold. There are 4 of those lifters per side. The heads need to be removed to replace so I would only replace the passengers side at this time.
Absolutely. The first action of the stability system is to cut engine power. If there's a problem with the engine, it disables the stability system.
I just double checked, there is an update to the bulletin about this. The latest fix is to replace the lifters, replace the oil pump and oil pan. See the attached bulletin.
No, just the lifters, gaskets for head, exhaust and which ever else is opened.