Let’s talk about misfire codes, specifically “P0316: Engine Misfire Detected on Startup (First 1000 Revolutions)”. What does this code mean, and how do you diagnose the root cause?
Around the 2006 model year, cold start emissions monitoring became mandatory here in the US. Before this mandate, emissions monitoring wouldn’t begin until after the engine reached operating temperature, and it entered into closed loop fueling. Oxygen sensors are the primary device for emissions monitoring, but they are inactive when the engine is cold. They simply aren’t reliable for cold start monitoring.
However, the misfire monitor is working from the first revolution of the engine. This monitor uses the crankshaft position sensor to measure crankshaft acceleration, then it compares the acceleration readings for each cylinder. A misfiring cylinder will produce a slower crankshaft acceleration speed. The monitor will recognize this and illuminate the check engine light.
There are a number of possible causes for this code to be set. Start with the basics: fuel, compression, and spark. While it is possible for a set of old, worn out spark plugs to cause this code, it’s not the most likely reason. However, if that P0316 code is accompanied by other cylinder-specific misfire codes, the plugs, wires and/or coils could be a more likely culprit.
Winter blend fuel is probably the most common reason for this code, especially during the fall months as the gas stations start to transition between fuel blends.
A burned valve or valve seat could cause this code to set, this can easily be confirmed with compression and cylinder leak-down tests. A faulty head gasket could leak coolant into the cylinder, causing a misfire immediately upon startup. Once that coolant works its way out of the engine, the misfire would go away. Customers may notice that they’re having to fill the coolant tank but there are no external leaks on the engine.
This video is sponsored by Autolite