2015 Tahoe P0300 Random Misfire - Rough Idle and Stalling

Question

My Tahoe started idling really rough yesterday and the check engine light started flashing when I get on the freeway. It feels like it's losing power under load and almost stalled at a stoplight this morning. I can smell a bit of raw exhaust but don't see any smoke.

Brian O'Connor · Accepted Answer

The issue turned out to be a failed lifter on cylinder 4 which is common with the Active Fuel Management (AFM) system. I had to pull the head and replace the lifter and the VLOM tray. Total cost for parts including the GM lifter (part #12680750) and head gasket set was about $650 in the driveway. While I was in there, I installed an AFM/DFM disabler to prevent it from happening on the other cylinders.

garagegrease · Answer

On these L83 engines, you should check your intake manifold bolts. They are known to vibrate loose over time, causing a vacuum leak that leads to a lean condition and a random misfire code.

shoptech_carlos · Answer

If the light is flashing, you're potentially damaging the catalytic converters. Check your freeze frame data to see if the misfires are happening on specific cylinders or across both banks to rule out a fuel pump issue.

Jake Morrison · Answer

Check the fuel injectors. These direct injection units are prone to carbon buildup or failure, especially on high mileage trucks if top-tier fuel hasn't been used consistently.

2015 Tahoe P0300 Random Misfire - Rough Idle and Stalling

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