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Driving home from work I decided to take the highway. The entry ramp I was on was very short so I stepped on the gas a bit to meet the speed of traffic. The truck began to sputter and shake, check engine light flashing and reduced power. Only a few moments later the light turned off and the truck began to run as normal but had a loud intermittent knocking noise coming from engine. Hooked up my code reader and saw a code for cylinder 3 misfire.
Did some research online and found A history of Active fuel management (AFM) lifter failure on GM engines. Cylinder 3 is a AFM cylinder. Removed the valve covers to inspect for a collapsed lifter but saw no issues. The truck was no longer under warranty so I decided to remove the cylinder heads to inspect further. Upon removing the lifters I found damage to the cylinder #3 lifter and damage to camshaft lobe. These AFM lifters are notorious for collapsing during a "miss timed switch event" from 4 cylinder mode to 6.
So now here I am with stuck fixing this far too expensive truck that I've only owned for 8 months. My word of caution to you is if you're dead on set on purchasing one these trucks do one of following.
Buy A tuner to completely deactivate the Active fuel management system. Or make damn well sure you have a excellent power train warranty.
- Chase M.,
Battle Creek, MI, US