2015 Tahoe P0300 Random Misfire and Stutter under load

Question

My Tahoe started shaking pretty bad when I try to accelerate on the highway or climb a slight grade. It feels like a constant stuttering but the check engine light is only flashing occasionally and then stays solid. It runs okay at idle but definitely lacks power when I step on it.

Lina Brooks · Accepted Answer

The issue ended up being a failed high-pressure fuel pump (HPFP) located under the intake manifold. Even though I had pressure at the rail, the pump couldn't keep up with demand under load. I replaced the pump (part #12683039) and the required high-pressure fuel pipe (#12677002). Torque the pump bolts to 18 ft-lbs and the fuel line nuts to 22 ft-lbs; the truck pulls hard again with no more codes.

wrenchqueen · Answer

Check for a cracked porcelain on the new plugs you installed. It is very easy to crack them on these tight Chevy heads if you don't use a swivel socket, which will cause a spark arc to the manifold.

Chris Donovan · Answer

On these L83 engines, you should check your long-term fuel trims. If you see them high on both banks, you might have a vacuum leak at the intake manifold gaskets or a cracked air intake boot after the MAF sensor.

torque_terry · Answer

Since you have P0171/P0174 codes along with the misfire, it's definitely a lean condition. Check your fuel pressure; the high-pressure fuel pump (HPFP) on the back of the engine is known to fail and cause these exact symptoms under load.

2015 Tahoe P0300 Random Misfire and Stutter under load

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