A year red flag Century Star car, the engine is Nissan type, mileage often appears in summer hot car is difficult to start. The fault was verified after receiving the vehicle, and at the same time it was observed that the exhaust pipe did not smoke. Connect the fault detector to detect, no trouble code display. Taking into account the normal operation of the vehicle, it shows that the intake, exhaust, fuel supply and ignition system performance is basically normal. Since the exhaust pipe does not emit black smoke, it is important to check whether the carbon in the intake manifold is carbon black. Disassemble the injector, observe the interior of the intake manifold from the installation hole, and see the thick carbon deposited on the wall of the tube, and it is found that there are heavy charcoal on the back of the intake door. Clean up the coke and repair it after trial run, troubleshooting. The reason for the analysis is that carbon deposits adsorbed part of the fuel, resulting in excessive dilution of the mixture into the cylinder, resulting in difficulty in starting.