The engine of a speed machine can misfire for a list of faults. It happens when the internal combustion in the cylinder is not properly carried out. Air to fuel ratio imbalance, ignition system issues, transmission issues, and other mechanical faults- can cause the engine to misfire. The engine is stumbling means you are driving with a misfired engine. The rate of stumbling as well as jerking depends on the severity of the misfire. Replacing the ignition coil or the distributor, fixing the intake manifold leaks if any, keeping the spark plug clean- can help you to get rid of the engine misfiring problem.