- Are there any noticeable leaks in the fuel lines?
- Have you disconnected and then reconnected the wire connectors several times? Corrosion or unprofessional handling can damage the contacts.
- Carefully inspect the connectors of individual injection system units. Do not bend the contacts, just treat them with contact spray.
- If the engine is not running smoothly at idle, check to see if the engine is sucking in additional air.
Finding the place where the "additional air" comes in
Leaky sections of the air intake system let in so-called additional air, i.e. air that is not included in the calculation of the control unit and therefore significantly disrupts the process of preparing the fuel-working mixture. The amount of fuel in the working mixture decreases uncontrollably. This disruption is most noticeable at idle speed by fluctuations in the number of revolutions.
1. Check the vacuum hoses for cracks and tightness. Check all hoses connected to the intake manifold (for example, from the brake booster, from the fuel pressure regulator, the electromagnetic valve of the system, the fuel vapor collection/return system).
2. Warm up the engine, then, leaving it idling, open the hood.
3. Apply starting fuel from a spray bottle (e.g, "Startpilot") throttle valve pipe, flange gaskets, intake ports and pipes to units controlled by means of reduced pressure. To do this, disconnect the lambda probe connector.
4. If the number of revolutions changes when spraying a certain place, then a leaky area has been detected.