Easy step by step guide on how to tune up an automotive engine,
though each engine configuration is different the process is similar.
Difficulty Scale: 5 of 10
Begin with the car on level ground, in park with the emergency brake set.
- Many times an engine tune up can be accompanied
by a check engine or service engine soon light. If this is the case, connect a
trouble code reader to
retrieve diagnostic trouble codes
to isolate the misfiring cylinder or malfunctioning
Step 2 - A fuel filter is used to clean fuel before
it enters the fuel injection system. This filter should be
within an engine tune up. (Note: Some vehicles are not equipped with the an external
filter, these vehicles filter is located inside the fuel tank and are good for the
life of the car in most cases.)
Step 3 - A mass air flow sensor measures engine
air intake volume while generating data for the computer. This sensor processes
large amounts of air and after many miles of usage, the sensor element becomes contaminated
and must be cleaned
using a sensor safe carb spray.
Step 4 - An engine air filter is designed to remove
dirt and other contaminants from the air intake system, inspect and
the air filter
Mass Air Flow Sensor
Step 5 - A throttle bore actuator is used to control
air flow into the engine's intake manifold, and onto each cylinder. Manually controlled
units (throttle cable) use an idle air control valve (IAC) to adjust engine idle
speed. These devices process large amounts of air much like the mass airflow sensor.
After many miles of operation a condition called coking occurs which hinders performance
characteristics. These items must be
Engine Air Filter
(cleaned) to operate correctly.
Step 6 - A spark plug is used to ignite the fuel
air mixture inside the engine's combustion chamber via the ignition coil. Begin
by locating the spark plug and spark plug wire or coil, (COP, coil over plug.)
Engine Throttle Bore w/Idle Air Controller
Step 7 - After the spark plugs have been located,
remove the ignition coil electrical connector.
Spark Plug Location - Coil Over Plug (COP)
Step 8 - Once the electrical connector has been
removed, located and remove the coil mounting bolt.
Remove Coil Connector
Step 9 - Then, gently remove the ignition oil from
the spark plug well, while talking note of any coil damage or motor oil. (Note:
If motor oil is present the valve cover gaskets has failed.)
Removing Coil Mounting Bolt
Step 10 - After the coil has been removed, inspect
the coil for dark or light markings which indicates electrical leakage failure and
must be replaced.
Removing Ignition Coil
Step 11 - Inspect coil electrical terminals for
corrosion or signs of heat which indicates failure.
Ignition Coil Removed
Step 12 - Once the coil has been removed, use a
spark plug socket and extension to remove the spark plug. (Note: A spark plug socket
is rubber lined as to not damage the plug.)
Coil Electrical Terminals
Step 13 - Using a socket wrench, turn the plug
counterclockwise to remove it from the well.
Spark Plug Socket
Step 14 - After loosening the plug, carefully remove
it to inspect. This inspection can give information on how that particular cylinder
is running. If the plug is white, or slightly yellow with little flecks of gray
or black the cylinder is running pretty well. If the plug is wet with fuel, the
cylinder is not firing, this could be
Removing Spark Plug
or a faulty
. If the plug is covered in black soot, the mixture is extremely rich indicating
on opposing cylinders.
Step 15 - Once removed, match the new replacement
spark plug to the old plug. Its important to install the correct plug or the engines
performance will be hindered. Also check the plug "gap" which should be consistent
and to the manufacturer recommendations.
Spark Plug Removed
Step 16 - After the right plug has been identified,
with the correct gap measurement, gently insert the plug into the socket.
New Spark Plug
Step 17 - Next, gently lower the spark plug down
in to the plug well. This is an important step because if the plug is bounced, or
dropped, it can close the plug gap or damage the plug causing a misfire or poor
Insert New Spark Plug
Step 18 - Once successfully lowered into the plug
well and rolled in by hand, attach a ratchet and tighten the plug. The tighten specification
can vary, but a general rule of thumb is to crush the sealing ring about half way.
Insert Spark Plug Into Plug Well
Step 19 - After the spark plug is tight, reinstall
the coil into the plug well, making sure the end of the coil is over the spark plug.
Tighten Spark Plug
Step 20 - Then, install the coil mounting bolt
Reinstall Ignition Coil
Step 21 - After the coil mounting bolt is tight,
reinstall the coil electrical connector and repeat this process throughout the remaining
Tighten Coil Mounting Bolt
Once completed, start the engine and observe the performance, if obvious problems
exist retrace the previous steps to discover a damaged spark plug, ignition coil,
or plug wire not correctly installed.
Vehicles are equipped with many different styles of ignition systems, but all
follow the same principle. A tune up is needed between 35,000 to 75,000 miles depending
on driving conditions and car manufacturers recommendations. Before starting, determine
the individual tune up parts. When performing a tune up avoid contact with undesirable
components such as exhaust manifolds, serpentine belts etc.)
Most spark plug gaps are pre-set and ready to install. Replace spark plug wires
individually to avoid confusion, mark the wires clearly while confirming proper
length of each wire, twist the wire boot to help break the seal which will assist
in the wire removal. Inspect coil output terminals for corrosion as this will hinder
The spark plug gap is important because it determines the amount of resistance
used to "time" the
Reinstalling Coil Electrical Connector
. An incorrect spark plug gap can cause
and poor mileage.
The condition called "coking" can cause stalling as well as variable idle ranges.
Tools and Supplies Needed
- Spark plug socket
- Carburetor cleaner
- Shop towels
- Fuel filter release tool (some models)
- Spark plugs
- Fuel filter
- Air filter
- Plug wire set (some models)
- Screwdriver set
- Protective gloves and eye wear
- Remove debris from the spark
plug well using compressed air.
- Inspect the new spark plug porcelain and isolator before installing.
- Use OEM (original equipment manufacturer) parts to ensure proper performance.
Article first published 2016-02-05