What is the reason for the serious idle jitter of Peugeot 408 engine?

The reason is that the engine has serious carbon deposition and the ignition system has problems.

First, the engine has serious carbon deposition.

When the engine has too much carbon deposit, it will cause idling jitter after cold start. This is because when there is too much carbon deposit, especially when a large amount of ejected carbon is absorbed by the carbon deposit, the mixture will be too thin and it will be difficult to start.

At this time, you can only wait for the mixture to reach a certain level before starting the car, but at this time, the mixture in the cylinder will become thicker due to excessive carbon deposition, and the engine will shake at this time.

Second, the ignition system problem

Problems with the ignition system can also lead to idle jitter, which is also due to excessive carbon deposition in the spark plug.

Inspection and elimination methods of automobile jitter fault

1, inspection of idle speed control motor

Turn on the ignition switch to 1, and you should be able to hear the motor. If there is no sound, repair or replace the idle speed control motor, ECU and related circuits; If there is a sound, continue to the next step.

2. Inspection of throttle potentiometer

Measure the voltage between pins 8 and 7 of throttle control unit, which should be 3. 8V or so, and does not change with the change of throttle.

If the voltage is abnormal, repair or replace the throttle positioning potentiometer. If the voltage is normal, check the wiring between the throttle position potentiometer and ECU. If the circuit is normal, repair or replace ECU；; If the wiring is abnormal, repair or replace the wiring. Check whether the vacuum pipe connection between the fuel distributor and the throttle body is good.