An engine tune-up used to be equal parts art and science. It can involve manually tuning the carburetor, setting the timing and maybe even adjusting a set of points. However modern cars are equipped with sophisticated engine management systems that adjust every aspect of combustion on the fly.
Such advancements have streamlined many aspects of the traditional tune-up, but they've also introduced a new set of challenges for the DIYer to navigate.
Our Tinker experts have created this helpful engine tune-up guide to walk you through some of the lesser-known steps you can take to improve the overall health of your modern engine and keep it performing at its best over the long haul.
Before you install brand-new spark plugs, always double-check the gap, which is the small space between the two electrodes at the end of each spark plug. These days, most new spark plugs come from the store pre-gapped, but don't throw away your spark plug gap tool quite yet. You may need to make some small tweaks to match the exact specs for your engine. If the gap is too wide or too narrow, it can cause a multitude of problems, including misfires and poor fuel economy.
In the past, DIYers would apply anti-seize compound to the threads of their spark plugs to prevent them from getting stuck in the cylinder head. Most spark plugs now come with a silver corrosion resistant coating on the threads that makes this messy step unnecessary. In fact, using anti-seize can throw off the readings on your torque wrench, potentially leading you to over-tighten and damage the plugs.
While you have the spark plugs out, it's a great time to dive a little deeper into the health of your engine with a compression check. This is a relatively simple process involving a compression test kit and, ideally, two people – one to crank the engine with the ignition and the other to monitor the readings.
Uniform pressure readings across all cylinders – typically of at least 130 pounds per square inch (PSI) – is what you're looking for. This indicates that the valves, piston rings and cylinder walls are all in good condition and working harmoniously.
Variations of more than 10% from one cylinder to the next, however, signify problems. Especially readings under 100 PSI. Such low compression can be the result of worn rings, scored cylinder walls or valves failing to seal properly – all conditions that lead to reduced performance, increased oil consumption and eventually catastrophic engine damage. Identifying them early will give you a chance to address them before things get worse.
Your engine’s Mass Airflow Sensor (MAF) measures the volume and density of air entering the engine. This information helps the Engine Control Unit (ECU) optimize fuel injection rates for smooth and efficient operation.
Over time, however, dust and debris can accumulate on the MAF sensor and cause inaccurate readings, which can lead to a range of engine performance issues, including rough idling, stalling and poor fuel efficiency.
Fortunately, cleaning your MAF sensor is an easy job for a DIYer. It's typically found in the air intake, between the air filter and the throttle body. Disconnect it carefully, then use a specialized MAF sensor cleaner spray, which is available at most auto parts stores. While handling the sensor, avoid contaminating its delicate wires with oil from your hands. Reinstall it when it’s dry.
Your oxygen (O2) sensor checks oxygen levels in the gases exiting your engine through the exhaust. This data allows the engine control unit (ECU) to fine-tune the air-fuel mixture for optimal combustion.
Like all electrical components, O2 sensors degrade over time, leading to inaccurate readings and, as a result, diminished engine output and efficiency. Changing your O2 sensor every 60,000-90,000 miles can avert these issues, not to mention prevent an emissions test failure.
With the engine off and cool, locate the sensor within the exhaust system, typically near the catalytic converter. Disconnect its electrical connector and unscrew it with an O2 sensor socket, which is available at any auto parts store. Next, thread in the new sensor by hand to prevent cross-threading and secure it with the socket before reconnecting it.
The fuel filter tends to get overlooked in routine maintenance, probably because it's typically hidden away at the back of the car, near or even in the gas tank. But the role it plays isn't trivial. As the name implies, it ensures that only clean, debris-free fuel reaches the combustion chamber.
With age, fuel filters can become clogged with silt, rust and other contaminants, eventually starving the engine of fuel. Symptoms of a dirty fuel filter include difficulty starting, sluggish performance and occasional stalling. A dirty filter also forces the fuel pump to work harder, shortening the lifespan of this expensive-to-replace part.
The process of changing the fuel filter varies from car to car, so be sure to consult your owner's manual before tackling any job. A good rule of thumb is to replace it every two years or 30,000 miles. Be sure to write the date and mileage on the outside of the new filter so you'll remember when the next replacement is due.
Have a specific aspect of car maintenance you'd like us to cover next? Feel free to share your suggestions and shoot us an email at support@tinkerdiy.com, and we'll consider them for our upcoming guides!
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