What should be replaced in a tune up

The ignition system is comprised of many individual sensors and other parts. The ignition system provides the spark for each cylinder spark plug, at the correct time, causing the cylinder to fire the mixture of compressed air and fuel.

The major components are the computer, coils, spark plugs, plug wires, numerous sensors, and a battery. You can expect to do repairs to the ignition system that is not a tune-up.

There is no set maintenance schedule for ignition system repairs other than a tune-up. Ignition system failures generally will set the check engine light. So in and of itself the tune-up is not rocket science, but other ignition system repairs can be difficult to diagnose. Another compounding factor is what other repairs that might be required in the near term that may share labor time. Ignition systems have many moving and electronic parts; are complicated, and many failures exhibit the same symptoms.

The fact that there are repairs to the ignition, that many call a tune-up, can make it even more confusing. These ignition system repairs generally require a diagnostics test following a protocol shown in our diagnostics library. The recommended tune-up does not require other things to be done with it, and is again considered preventive maintenance, requiring no diagnostics.

The fuel system is also comprised of many individual sensors and other parts. The fuel system provides the fuel mixed with air to each cylinder at the correct time to be ignited by the ignition system. The ignition system and fuel system work together and their repair and maintenance can get very intermingled and or confusing.

As with the ignition system, failures is this system will generally set the check engine light. The major components are the fuel pump, fuel filter, air cleaner, throttle body, intake manifold, injectors, fuel regulator, and computer. The only preventive maintenance procedure in the fuel system is the fuel and air filters.

The replacement times are listed in the recommended maintenance schedule. Yes, the ignition and fuel systems share the same computer. The troubleshooting of these two systems requires experience, special equipment, and diagnostic data support. The poor old fuel filter perhaps is the most neglected part on the average car. When they go bad the result can cause premature fuel pump failure, the car may not run and can be a diagnostic nightmare.

In general its appearance on your dash is to inform you that the computer has detected a problem, requiring a repair to the ignition or fuel systems.

The problem is significant and caused by readings or sensing that is outside of the factory specifications. There are a couple hundred reasons for this light to be on, each being called a fault code. Each fault code has a diagnostic procedure that is many steps long and can lead to many different recommended repairs. Not all fault codes will generate a customer complaint, so the first thing a good mechanic will ask about is what the observations of the customer are.

As long as your vehicle is running properly, has full power, the alternator light not on, and not overheating you may proceed and get it scanned at your earliest convenience.

If the car is not running right, immediate attention is required. Yes, there are some cases when the check engine light repair can be deferred till a better time. Then again there are fault codes that must be fixed very soon, if not immediately. If the check engine light is flashing at you, the engine has a serious misfire and must be repaired immediately, to prevent destroying the very expensive catalytic converter. Each fault code falls into three categories.

It is still recorded in the computer for future diagnostic support. The second type of fault code is called a current hard code. The computer is getting sensing consistently out of specification. The third type of fault code is called a historic fault. There was a time when sensing were out of specifications, but in the past. Most historic codes turn off the check engine after a specified number of drive cycles. Not all fault codes turn on the check engine light, but are still recorded in the computer for diagnostic purposes.

When your car is running poorly and the check engine light is on we recommend that your vehicle be diagnosed and repaired. The reason being, when your car is running poorly it is causing other damage that will cost you even more latter. There are at least three, if not five computers in the modern vehicle. All set fault codes, many of them not being allowed to turn on the check engine light.

Some of these codes are so important that additional lights have now been placed in your dash. The electrodes are made of tough platinum or gold-palladium alloys that resist erosion. Such plugs may go , miles under optimum conditions no fouling. Of course, no plug will last anywhere near its potential lifespan if an engine is burning oil, experiencing abnormal combustion such as detonation or preignition, or has a fouling problem. Though many motorists don't even know what an oxygen sensor is, let alone that their engine may have one or more of these devices, the fact remains that sluggish O2 sensors cause a lot of driveability problems.

To prevent such woes, the O2 sensor can be replaced for preventive maintenance during a tune-up. Unheated 1 or 2 wire wire O2 sensors on through early s applications should be replaced for preventative maintenance every 30, to 50, miles.

Heated 3 and 4-wire O2 sensors on mids through mids applications should be changed every 60, miles. And on OBDII equipped vehicles all '96 and newer , the recommended replacement interval is , miles. The O2 sensor is the master switch in the fuel control feedback loop. The sensor monitors the amount of unburned oxygen in the exhaust and produces a voltage signal that varies from about 0.

The computer uses the O2 sensor's signal to constantly fine tune and flip-flop the fuel mixture so the catalytic converter can do its job and clean the exhaust. If the O2 sensor circuit opens, shorts or goes out of range, it usually sets a fault code and illuminates the Check Engine or Malfunction Indicator Lamp. But many an O2 sensor that is badly degraded will continue to function well enough not to set a fault code but not well enough to prevent an increase in emissions and fuel consumption.

So the absence of a fault code or warning lamp doesn't mean the O2 sensor is doing its job. Deterioration of the O2 sensor can be caused by a variety of substances that find their way into the exhaust such as lead, silicone, sulfur, even oil ash as well as environmental factors such as water, splash from road salt, oil and dirt. A sluggish sensor may not allow the computer to flip-flop the fuel mixture fast enough to keep emissions within acceptable limits.

A dead sensor will causes the system to go back into open loop with a fixed, rich fuel mixture. Fuel consumption and emissions go up, and the converter may suffer damage if it overheats.

Something else that should be part of a tune-up today is cleaning the fuel injectors and intake system. The need for injector cleaning isn't as great as it once was thanks to improved fuel additives and redesigned injectors. But in areas that have gone to reformulated gasoline, injector clogging is on the rise again.

The result can be lean misfire and a general deterioration in engine performance and responsiveness. Deposits can also build up on the backs of intake valves, causing cold hesitation problems in many engines.

The cure is to clean the injectors and valves. Cleaning should is recommended for any engine that is suffering a performance complaint or has more than 50, miles on the odometer. That being said, regular tune-ups can prevent the types of mechanical issues that cause major engine problems.

A tune-up will prevent issues that could keep your car in the shop for weeks and cost hundred or even thousands of dollars. Any replacement parts or repairs will require an additional fee. Consider this money an investment in your vehicle and insurance against future repair bills. Beginner Driver's Guide. Car Maintenance. Pass your driver's test. Be fully prepared in days, not weeks with Premium. It can also make regular services a lot cheaper.

The bottom line is that if something unusual starts to happen with your vehicle, you need to take it to an auto care professional to get a proper diagnosis. A: This usually depends on the regular scheduled maintenance recommended by your car manufacturer, but usually older vehicles with non-electronic ignitions should be tuned every 10, to 12, miles or every year.

If your car is newer and has an electronic ignition and fuel injection, then you can go from 25, to as many as , miles without needing a major tune-up. A: The major benefit of an auto tune up is that it ensures your car functions properly and it prevents further damage. A: An auto-tune up will certainly help your car run better, but proper maintenance and regular servicing are also important.