The mileage is over 200 thousand km, the V8 engine is used, the displacement is 4.0L, the model is 3UZ-FE, and the 2005 Lexus LS400 cars are equipped with the 4 speed automatic transmission. User reflection: the car has the exhaust pipe black smoke, the idle speed is unstable, the acceleration is weak and there is the phenomenon of firing, three yuan catalytic device burning red, and the failure of the light of the CHECK lamp. Inspection and analysis: first, the fault code of the TE1 and E1 terminals of the engine compartment connector is read at 26, that is, the air-fuel ratio is too high. So the air filter was removed, and the trouble remained. Then check the fuel pressure of the oil supply system, the results are normal, the oil pressure is about 255kPa at idle speed, and the vacuum hose on the fuel pressure regulator is dismantled. The oil pressure is 304kPa and it is normal. It was found that the spark plug of each cylinder was checked and the 2, 3, 5 and 8 cylinder spark plugs were all carbon, while the 1, 4, 6 and 7 cylinder spark plugs were normal, so the ignition tests of 2, 3, 5 and 8 cylinders were made, and all the ignition was too weak. It is preliminarily determined that there is a problem with the second ignition coil or the second igniter for ignition of the 2, 3, 5 and 8 cylinders. First, simply replace the No. second ignitor with the first igniter, and the fault is still the same. Check No. second ignition coil, the primary coil resistance is 0.5N, the secondary coil resistance is 11kn, all meet the requirements, the No. second ignition coil and the first ignition coil change, then 2, 3, 5 and 8 cylinder ignition normal. So the No. second ignition coil is out of question. Troubleshooting: replace No. second point coil, after trial run, troubleshooting. Fault summary: the LS400 engine ignition system consists of 2 sets of igniter and ignition coil, No. first igniter and No. first ignition coil control 1, 4, 6 and 7 cylinders, and second igniter and second ignition coil control 2, 3, 5 and 8 cylinder ignition. In this case, the ignition of the No. second ignition coil is poor, causing the 2, 3, 5 and 8 cylinders to ignite too weakly, and the mixture combustion is incomplete, which is consistent with the output fault code 26. However, because the ignition coil No. second can still ignite, it will not output fault code 15 (that is, second ignition system failure). After that, the car owner confirmed that the car was in the engine system after cleaning up the above failure, so the cleaning of the engine is the direct cause of the damage of the ignition coil.