BE. Mechanical Overview

BE. Mechanical overview




Air and vacuum hose leakage
If the intake hoses leak the engine will normally get too much air. This will affect several electrical components; the IAC valve and H028 for example.
Driving with leaking hoses can cause one of the adaptive fuel trim (adaptive HO2S control) DTCs (2-3-1, 2-3-2) to be logged.

Air filter/air Intake.
A clogged air filter/air intake will mean that the engine does not get enough air. This occurs during acceleration and at high loads.




The exhaust system
Because of pressure pulses air will enter the exhaust system If It is leaking. If the leak occurs before the H028 the outside air will affect the sensor, making it think that the engine is running on a weak mixture. This in turn will affect the adaptive fuel trim.
The result of driving with a leaking exhaust system may be that one of the adaptive fuel trim DTCs (2-3-1, 2-3-2) is logged.




Injectors
If one or more Injectors are clogged the engine will not receive enough fuel. The mixture will be too weak which in turn will affect the fuel trim.
Driving with clogged injectors can cause one of the adaptive fuel trim DTCs (2-3-1, 2-3-2) to be logged.




Fuel pressure
It is important that fuel pressure is as specified so that the correct volume of fuel is injected. If the fuel pressure is too low the mixture will be too weak and if fuel pressure is too high too much fuel will be injected.
Driving with too low/high a fuel pressure can cause adaptive fuel trim DTCs (2-3-1, 2-3-2) to be logged.

Residual pressure
If residual pressure is low this indicates that the pressure regulator or an injector/cold start valve is leaking.
Starting problems may occur when the engine is warm. Driving with leaking injectors can cause adaptive fuel trim DTCs (2-3-1, 2-3-2) to be logged.




Fuel filter
A clogged fuel filter will result in fuel pressure being too low. See fuel pressure and residual pressure.
Driving with too low a fuel pressure can cause adaptive fuel trim DTCs (2-3-1, 2-3-2) to be logged.

Fuel pump (FP)/Tank pump
A poor FP/tank pump will result in fuel pressure being too low. See fuel pressure and residual pressure.
Driving with too low a fuel pressure can cause adaptive fuel trim DTCs (2-3-1, 2-3-2) to be logged.




Evaporative Emission (EVAP) system
A defective EVAP system will allow fuel fumes to be sucked into the engine unchecked.
Driving with a badly operating EVAP system can cause the adaptive fuel trim DTC 2-3-1 to be logged.




Throttle body (TB) and pulley
If there is too much choke on the throttle the engine will get too little air and may stop. If the throttle is set too high fuel fumes will be sucked in via the EVAP system making the mixture too rich.

Fuel quality
Fuel should not be contaminated by dirt or water. Poor fuel quality may lead to starting and driving problems.




Idle switch
If the idle switch is incorrectly adjusted so that the control module does not receive the information that the throttle is in the idle position idling speed is not controlled by the IAC valve. If there is no idle switch the engine will only receive air via the throttle when it is started. If the throttle is correctly adjusted idle speed will be about 500 rpm. If the throttle is set too weak the engine will get too little air and may not idle.




Valves
Incorrect valve play, worn or burnt valves can result In poor acceleration and sluggish or uneven performance which is most noticeable when the engine is idling.

Compression
Uneven compression may lead to poor acceleration and sluggish engine or uneven performance which is most noticeable when the engine is idling.




Camshaft adjustment
If the camshaft is incorrectly adjusted relative to the crank- shaft the valves will open too early or too late. This will make the engine sluggish and prevent it from picking up speed.




Crankcase ventilation
The crankcase ventilation is connected to the intake manifold in order to suck In crankcase fumes. If the oil level is too high or the oil is contaminated with fuel the fuel/air mixture will be too rich which will affect the adaptive fuel trim.
Driving with contaminated engine oil can cause one of the adaptive fuel trim DTCs (2-3-1, 2-3-2) to be logged.




Drive plate/Flywheel
If the drive plate/flywheel are uneven or damaged the RPM sensor will send an Incorrect signal to the control module.
The drive plate is very susceptible to mechanical damage. Never use the drive plate to turn the engine or as a counterhold.
A damaged drive plate will cause the engine not to start, to be hard to start, to run unevenly or to stop.

Spark plugs
Worn spark plugs result In poor combustion in the cylinders which will manifest itself as an uneven idling speed and increased hydrocarbon readings.




Ignition leads/distributor/rotor
Cracks in the distributor/rotor or damaged ignition leads will lead to poor combustion in the engine which will be most noticeable because of the sluggish engine, uneven idle speed and significantly increased hydrocarbon readings.

Rotor
Cracks or too high a resistance in the rotor will result in the engine not running on all cylinders leading to poor combustion. This is most noticeable because of the sluggish engine, uneven idle speed and significantly increased hydrocarbon readings.