2015 Corvette Z51 p0300, several misfires, mostly the V4 mode cylinders.

Hello everyone, I’m new to the site, and find Matt’s videos spot on. This thread will have a long and perhaps boring thread, first to describe the issue, and then what we will do to find the root cause.

Several of us have C7 Corvettes and routinely participate in HPDE events at road course tracks. One of our “clan” has been having a lot of trouble with his car. When he runs at sustained high speeds, he develops misfire codes which ultimately puts the car in “limp mode”. The car is under warranty, so the car has been to the dealer, where the “parts cannon has been fired at the car many times. the dealer has replaced valve springs, lifters, the ECM, and several other parts. Some of the events have been at the direction of the next level at GM beyond the dealer. Sadly, all was a waste. One thing that did change was when the ECM was changed, the misfires MOVED to the opposite two V4 mode cylinders! As an additional note, the most frequent misfires happen with the V4 mode cylinders, with fewer at all cylinders. The misfire count causing a P0300 might logically be caused by the V4 cylinders. When he is on the track, and the car set to track mode, the V4 is deactivated. However, the misfires occur whether in touring mode, or track mode.

When we were all at the Corvette Caravan at the NCM in August, top level GM folks listened to the issue description. One person stepped up and declared he would source a data logger to the dealership to log sensor data to figure out what is wrong.

Of course, that has yet to happen. The strike, and exposure to the element administratium has bogged this offer down in some way.

I have an an Autoenginuity scan tool with enhanced GM, and a Corvette Service manual. The owner is bringing his car to my shop and we are going to set about to create a datalog to see if sense can be made of all this. (I’m a hard-core DIY}

I suspect something is going on with the crank sensor and maybe cam sensors. Surely the dealer tech has at least looked at the Crank sensor and wiring. Maybe not, it is tucked in above the starter and the wiring harness from it routes really close to the front CAT. If we can, we are going to at least check continuity on the wires and look for heat damage.

So, if anyone has ideas to share we are all ears. Particularly, if you have an idea of which sensors to log, that would be a great help. Our attempt to set up data logging will happen Oct 28; in preparation for a track day at VIR Nov 7,8