Engine Tune-Up
By Jonathan Rollins

Tune – Up Procedures are done as part of a
routine maintenance rather than to correct a
drivability problem.
Wear safety glasses!
Spark plug replacement

Most new engines do not require spark
plug replacement for up to (100,000 miles)
Normal service and replacement items
in a minor tune-up are…










Perform a visual inspection for obvious problems
Check for trouble codes on computer controlled vehicles
Replace spark plugs
Service the ignition system, including checking secondary components
Replacing the air and fuel filter
Changing oil and lubricating the chassis
Testing and servicing emission control system, and resetting the reminder
circuit
Adjusting the fuel system if applicable
Cleaning the throttle body and idle air bypass on fuel injected engines
Road testing before and after tune-up to check engine performance
Service and replacement items in a
major tune-up are…









Perform a scope analysis of engine system
Testing and replacing spark plug wires
Testing and replacing fuel pump
Replacing drive belts
Replacing brake, transmission, and other fluids
Replacing or rebuilding the throttle body
Rebuilding or replacing the distributer
Adjusting the valve train (some engines)
Replacing weak sensors: oxygen sensor, cam position sensor, crank shaft
position sensor, ect
Six of the diagnostic tools
used during a tune-up are…
 scan
tool, an exhaust gas analyzer, a
compression gauge, a multi meter, an
oscilloscope, a vacuum gauge, and
other tools
Some performance factors affected by
a tune-up are…






Engine power acceleration
Fuel consumption
Exhaust emissions
Smoothness of engine operation
Ease of starting
Engine service life
General Tune-Up Rules

It is important to gather engine and vehicle
performance info before performing the
tune-up because this gives you clues on
what you need to investigate or replace.

It is important to bring the engine up to full
operating temperature prior to diagnosing
an operating condition because when the
engine is cold you cannot obtain accurate
test results.

Its important to maintain a vehicles service
records because if a problem occurs you
can check your record to correct the
trouble.
Tune-up safety rules

It is important for the battery to be
disconnected before maintenance so it
does not accidentally crank the engine or
electrical fire.
Tune-up safety rules to follow




Wear eye protection
Set parking break
Place vent hose on exhaust pipe
Disconnect battery
Typical tune-up procedures






Battery problems-dirty case top, corroded terminals, and physical damage
Air cleaner problems –clogged or contaminated filter, inoperative air flaps
or disconnected vacuum hoses.
Belt problems- looseness, fraying, and slippage.
Low fluid levels- engine oil, brake fluid, power steering fluid, ect.
Deteriorated hoses- hardened or softened cooling system, fuel system, and
vacuum hoses.
Poor electrical connections-loose or corroded connections : frayed,
pinched, or burned wiring and terminals.
Three important steps in replacing
spark-plug wires are…

To remove the spark-plug, first check that the spark-plug wires are
numbered or located correctly in their clips. Grasping the spark-plug wire
boot, pull the wire off the plug. Twist the boot back and forth if it sticks
Ignition coils must be numbered before plugs can or located correctly in
their clips. grasping the spark-plug wire boot, pull the wire off the plug.
Twist the boot back and forth if it sticks. Ignition coils must be removed
before plugs can be replaced. Be sure engine is cool before removing
spark-plugs. Removing a spark-plug from a warm aluminum head can
damage the threads in the spark-plugs holes.
Tools used to remove spark-plugs

Swivel ratchet, an extension, and a spark –
plug socket.
The correct colors for the tip and
insulator


Grayish or brown= properly burning
Black or wet= not firing or engine problem

If the spark-plug wire is not put on the right
cylinder spark-plug, the plug will not fire.
Oxygen sensors


One and two wires need to be replaced at
50,000-60,000 miles
Heated three-wire oxygen sensors should
be replaced at about 100,000 miles
Recommended procedures for
replacing a sensor

Disconnect the negative battery cable.
then, separate the sensor from the wiring
harness by unplugging the connector.
Never pull on the wires them selves, as
damage may result.
Three primary adjustments
performance during a tune-up



Pick up coil air gap adjustment
Idle speed adjustment
Ignition timing adjustment
Diesel engine tune-up

Diesel engines require periodic
maintenance similar to gasoline engines
but don’t have spark plugs to replace or an
ignition system.
Typical service tasks performed during
diesel engine maintenance intervals
are









Replacing the air filter element
Cleaning, draining, or replacing the fuel filters
Adjusting engine idle speed
Adjusting accelerator and governor linkage
Inspecting the engine and related systems
Adjusting valve and injector timing
Changing engine oil and oil filter
Servicing emission control systems
maintenance intervals are specific periods ( in miles or months ) for
component service.