Hey guys, welcome back to the ProjectDIY channel. In this one, we’re mobile again—because once again I’ve got a daughter with a car problem. Her 2010 Toyota Camry (with over 250k miles, closer to 275k) had a flashing check engine light, was running really bad, and wouldn’t go over about 50 mph. A flashing check engine light is a big clue for a misfire, and that can kick the car into limp mode to keep you from tearing something up if you keep driving it. I start it up at the gas station where she left it and you can feel it shaking. To find the dead cylinder, I unplug one coil at a time—when you unplug a good cylinder, the engine runs worse, but when you unplug the bad one, nothing changes. Once I found the cylinder, I narrowed it down to the usual suspects: coil, spark plug, or injector. My quick test is swapping coils between cylinders and seeing if the misfire follows the coil—and in this case, it did. I ran around and grabbed a replacement coil, popped it in, started it before tightening everything down, and the shake was gone. Car ran fine after that, and the main takeaway is simple: identify the cylinder, then switch those coils to confirm the bad one.