Fault phenomenon
    A Lexus LS400 passenger car (engine model 1UZ-FE), maintenance of the starter, the engine started after the flame, step accelerator pedal also stable. Related Reading: How to extend the engine gas distribution service life of the engine turbocharged intake system introduced
    Troubleshooting
    According to the fault phenomenon, the initial suspected oil problem. As the car is equipped with self-diagnostic system. First use the self-diagnostic function to diagnose the fault. In the engine compartment to find the detection of the diagnosis seat, with a short jumper diagnostic socket seat + B, FP terminal, found that the pump is working properly. Start the engine, with a stethoscope check the nozzle, action, sound normal, indicating that the oil condition is good. And then use the jumper to shorten the diagnosis of the seat of the TEl and E1 terminals, call the fault code, the engine fault indicator is displayed as 15 fault code, meaning "lGF2 '' signal is not sent to the engine computer.
    After analyzing the fault location may be:
    (1) 2 igniter or line failure
    (2) 2 ignition coil or line failure;
    (3) engine computer failure. Taking into account the car maintenance starter, the demolition of No. 2 ignition coil, and in the disassembly process, due to the aging of the plug, resulting in damage to the primary coil plug, loss of locking effect. So it is suspected that the ignition coil 2 is faulty. Then remove the No. 2 ignition coil inspection and found that the primary coil plug has a poor connection line, especially loose. After the start of the engine, the engine starts normal, refueling quickly, that troubleshooting.
    Ready to be delivered. The engine idling there is a regular ups and downs of the phenomenon. As in the maintenance of the starter process, disassembly of the intake chamber and intake manifold, cleaning the throttle body and idle stepper motor (also known as idling motor). And the car in the maintenance of the starter before there is no such phenomenon, after analysis that should start from the leak check. Along this line of thought, first check the vacuum tube with or without the phenomenon of leakage, after inspection did not find missing and broken vacuum tube. Check the vacuum with a vacuum gun and find the pointer between 45 ~ 60kPa beating back and forth (normal 56 ~ 66kPa), indicating that the vacuum can not hold, there are leaks. With carburetor cleaning agent spray throttle body, intake chamber and idle stepper motor interface seal, the engine speed does not change, indicating that these parts are not leaked place.
    So then. Where is the problem in the end? Is the intake manifold pad with air leakage caused by the phenomenon of idling? Replace the new intake manifold pad, the fault remains the same. Read the data stream with the gold Pentium "Colorful" decoder. It is found that the fuel injection pulse width is between 3.5 and 35ms (normally 2.5 ~ 35ms); the throttle opening is O ° (normal O ° ~ 6 °). Analyze from the data stream. Found that the engine idling speed is too high, fuel injection pulse width is too large, throttle opening is too small. The throttle opening adjustment at 3 °, the symptoms did not change. Then suspected throttle position sensor idle contact problems, the investigation of the idle contact is normal; and suspected air flow meter signal distortion, unplug the air flow meter plug, the symptoms did not change.
   At this time, I think it is probably a problem with idling stepper motor. So remove the intake hose and air flow meter, hand block the idling stepper motor bypass the majority of the inlet, start the engine, the engine idle speed, speed of 650r / min or so; and hand removed, the engine Idle and start the car again. This proves really because the idle stepper motor is faulty. Remove the idle stepper motor and check the resistance with a multimeter. Four sets of coil resistance are 50Ω (data standard 10 ~ 30Ω), the initial determination is the coil resistance is too large. Further check the operation of the idle stepping motor, connect the battery terminals B1 and B2, and then connect S1 → S2 → S3 → S4 and S4 → S3 → S2 → S1. Found that the spool only a slight sense of shock, spool does not work, so as to determine the car's idling stepper motor spool card damage.
    To verify this idea, replace the new idle stepper motor. The new idler stepper motor to do the same test, obviously see the spool toward the closing and opening direction of movement, check the coil resistance is 50Ω, indicating that the original idle stepper motor resistance is normal, but the motor spool Issuing cards. Install the engine with a new idle stepper motor. The engine is operating normally and the idle speed is steady. Troubleshooting.
    Maintenance summary
    (1) the engine can not start because the No. 2 ignition coil primary coil plug bad contact, resulting in the engine computer can not receive the ignition feedback signal "IGF2", the computer to determine the ignition system failure, for security protection. Command the nozzle to stop the fuel injection.
    (2) Idle speed is because the carburetor cleaning agent cleaning idle stepper motor method is not correct. After cleaning did not use compressed air blowing parts, resulting in idle stepper motor bearings lack of oil corrosion and coke precipitation caused by the spool card. After the engine is started, the engine computer detects that the engine speed is too high at idle conditions, thus instructing to reduce the fuel injection pulse width and the small idle stepping motor bypass air intake, but because the idle stepper motor spool card can not Action, resulting in excessive intake, speed down. Oxygen sensor to detect the mixed gas is too thin, this information will be passed to the engine computer, the engine computer to receive this information and then instructions to increase the fuel injection pulse width, so the engine speed and rise. So back and forth to adjust, and ultimately cause the engine speed between 1200 ~ 1400r / min operation, the engine idling tour.