How to Perform an Engine Tune-up

We are a team of ASE certified mechanics that have created this guide to help you save money while doing the job yourself, or at least see what you are paying for when having the job done at a shop. An engine tune up is required between 35,000 to 75,000 miles depending on driving conditions and the vehicle's  manufacturer recommendations. This service comprises many individual operations which we have listed below, this list can vary depending on engine ignition and fuel system designs.

What Goes Wrong?

As the engine operates service items such as, spark plugs, spark plug wires, ignition coils, throttle body, distributor cap and rotor, fuel and air filters start to wear or get dirty, and when left unattended can cause low power, engine misfires, limp mode, stall at idle, hesitation, hard starting or a check engine light.

What's The Cost?

When a tune up is performed there can be many variables which affect the parts and labor price. Some shops consider just a spark plug replacement as a tune up which by itself is incomplete, so it best to get a full list of what is included with the service, an engine oil change can be included as well. By looking under the hood you can see if the engine has coil over spark plugs (COP) set up that uses no spark plug wires, this is one configuration example which will cause price fluctuations. When purchasing tune up parts let it be known there are quality variables that affect price and the performance of each item. If exact times or procedures are needed you can ask our experts to supply you with the information (free), or consult an online resource such as AllData DIY (pay).

Let's Jump In!

1. Spark plugs are the most major part of a tune up which must be replaced without fail. Before removing the spark plugs use compressed air to clear the plug well free of dirt and debris which will help stop internal contamination of the cylinders. Remove the ignition coil or plug wire from the spark plug, if engine oil is present on the outside of the plug the valve cover gaskets need replacement. Most spark plug gaps are pre-set and ready to install but because of shipping conditions the gap can become mal-adjusted, confirm the proper gap by using a spark plug gap tool. Inspect the new spark plug's porcelain for cracks and isolator condition before installing (new spark plugs can be defective). If the ignition system uses plug wires, replace the spark plugs and wires one at a time to avoid confusion, mark the wires clearly while confirming proper length of each wire, also twist the plug wire boot to help break the seal which will assist in the wire removal.
   
2. After the ignition coil has been removed (COP systems), inspect the coil for dark or light markings which indicates electrical leakage failure warranting coil replacement, also inspect the coil low voltage electrical terminals for corrosion or signs of heat which indicates failure.
   
3. An ignition system can be constructed with an distributor cap and rotor which is responsible for distributing the ignition spark from the coil to the individual cylinders, over time the electrical terminals can become burnt and corroded and should be replaced as part of the tune up.
   
4. An engine processes large amounts of air while in operation, this will cause the throttle actuator to get dirty, a condition called Coking, this is where heavy air particles are left behind hindering the actuators performance. An engine tune up should include a throttle bore actuator cleaning service.
   
5. Manually controlled actuators use a throttle cable which utilizes an idle air control valve (IAC) to adjust engine idle speed via the engine computer. Much like the throttle bore actuator the IAC is subject to the Coking condition as well and should be cleaned within the tune up service to ensure proper operation.
   
6. The engine air filter is used to help keep dirty and debris from entering the engine, this too will become dirty which cases engine performance to suffer, inspect and replace the air filter as needed.
   
7. Some engines are equipped with a mass air flow sensor (MAF) which provides feedback information to the engine computer by monitoring the amount of air that enters the engine. This is also subject to Coking which contaminates the sensor wire located internally inside the sensor. Remove the sensor and use MAF cleaner to alleviate the sensor wire (hot wire) from dirt and air contaminants to help return the correct sensor operation.
   
8. Vehicles can be equipped with a serviceable fuel filter (not inside the fuel tank) which should be changed out during a tune up service. This fuel filter is used to remove fuel impurities before being processed through the fuel injectors allowing the fuel system to stay clean and trouble free. This filter is optional and will vary per vehicle manufacturer.
   

Questions?

Our certified technicians are ready to answer tune up questions for free. We hope you saved money and learned from this guide. We are creating a full set of car repair guides. Please subscribe to our 2CarPros YouTube channel and check back often for new videos which are uploaded regularly.