2014 GMC Sierra 1500 Misfire Code P0300 shakes and shudders

Eli Launius · October 11, 2022

Truck is shaking is shuttering at RPMs around 1300-1500 not necessarily at load but I guess you could kind of say it had some load on it. Took to dealership. Stuck a new spark plug wire on it and it seemed fine. Got it home drove maybe 30 extra minutes and it started back. Feels like a jerking type of motion but very slight when cruising down the road maybe 40-65mph. Doesn’t happen at high RPMs and high speeds. New transmission about 60k miles ago. All new spark plugs and wires about 6 months ago. I figured it was the lifters but it seems to be running fine at other speeds. Seems to have the number 5 as the main culprit but the other cylinders also randomly miss. I will tag some photos as well from today from my scan tool. Any help? Is not backfiring or I cannot tell atleast. No tunes on the truck. Regular 87 gas pumped. Every once and a while I will pump E85 but not really had any in a while. Driver side valve cover does have some sort of small oil leak. Maybe from crank case vaccum not really sure. Just wondering what y’all think.

Snowcamo · October 11, 2022

Pull the #5 plug wire off and use a roll of fine sand paper and clean the coil pack connector out. The plug wire connectors tend to push back over time if you do not twist them on to purge the air.

Thus the reason for the plug wire swap working. It made the connection a pinch better.

I had the same issue. The engine has a load the most at low rpm especially at take off.

To give you a more clear idea drive in tow mode and watch the issue go away if you stay in the 18k+ range. Little load from there up.

I would do them all. Cheap and easy.

Edited October 12, 2022 by Snowcamo