BMW X5: Engine Diagnosis
Engine Diagnosis
When attempting to diagnose driveability complaints, always consider the
basics. Regardless of the level of
technology employed on an engine, it still needs a few basic things to occur in
order to run properly. Whether
the engine is very basic or uses so-called "New Generation" technology always
refer to the basic principles first.
Any engine using four-cycle spark-ignition principles must meet the same
fundamental conditions to run
properly. Most engine related driveability problems fall into a few basic
categories:
- No Start/No Crank
- Extending cranking before engine start
- Rough Running Cold Idle
- Rough Running Warm Idle
- Rough Running Under Load
- Lack of Power
- Check Engine Light (MIL)
Fig. 1: Sectional View Of Engine
When referring to engine basics, all engines need fuel, air and spark to run.
However, in order for a spark-ignition
engine to run properly, a few things must be taken into consideration. The fuel,
air, spark principle can
be broken down further into the following categories:
- Sufficient engine compression with a leak-free combustion chamber.
- Sufficient amount of ignition voltage (spark) at the correct time.
- Proper fuel pressure and volume.
- Properly functioning fuel injection system (Engine management).
- Properly functioning air management system (Electronic throttle
systems).
- Correct valve timing (VVT and VANOS).
Fig. 2: Operation Of Valvetronic
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In order for an engine to run smoothly and efficiently, the combustion
chamber must be free of leakage. An
engine with low compression in one or more cylinders is inefficient and will run
rough or l
When performing cylinder leakage tests, the following tips might be helpful:
Remove all spark plugs to allow easier rotation of the engine. (If this test is
done after a compression test, the
plugs s
The ignition system on modern BMW engines consist of one ignition coil per
cylinder. This arrangement is
known as RZV, or Direct Stationary Ignition. The ignition coil receives fused
power usually f
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Fig. 3: Identifying Front Axle Components
A wheel/chassis alignment check must be carried out after the following work:
Release of following screw/bolt connections:
Steering gear to front axle carrier
Lower control arm to front axle carrier
Tie rod end to tie rod
Replacement of followi
IMPORTANT: Read and comply with notes on protection against
electrostatic damage (ESD
protection)
Necessary preliminary tasks:
Disconnect battery negative lead.
Remove front left wheel arch cover (rear section).
Release nut (1) and disconnect ground cable.
Disconnect plug connections (2).
Unc