Mass Air Flow Sensor

The mass air flow sensor (MAF) is used to monitor the amount of air going into the engine while running. Mass air flow sensors work in conjunction with the oxygen sensor and the engine control system to maximize performance and economy. A vehicles mass air flow sensor delivers a signal to the PCM (engine control module) telling the amount of air coming in, this is compared with oxygen levels in the exhaust to determine the efficiency of the engine. It is usually difficult to detect when a mass air flow sensor fails, the "check engine light" or engine symbol will probably not be illuminated. Your car, truck or SUV may have a poor idle quality, stall, low power or all three. Your PCM may have no trouble codes because the PCM cannot detect a problem since the sensor is working but is out of range.

Mass Air Flow Sensor

What has occurred with most MAF failures is the sensing element or "hot wire" that is used to give electronic feedback to the PCM for processing has become contaminated by air particulates. The mass air flow sensor is reporting to the PCM that less air is running through the engine than actually is. The PCM will then lean the fuel mixture down to the point that it will cause performance issues. There is not enough variance in the system to trigger a MIL "Check Engine" light so this particular repair problem can be difficult to detect through normal troubleshooting methods.

A mass air flow sensor is most common in newer vehicles, this sensor is used to help maximize efficiency and reduce emissions. One of the benefits of the mass air flow sensor is that it can respond to changes in air intake flow. There are no moving parts in a mass air flow sensor. Most vehicles mass air flow sensor locations are in the air intake for the engine, this allows easy replacement. It is recommended that the sensor be replaced approximately every 60,000 miles.

How Do I Tune Up My Car?

Most vehicles have ignition systems and a throttle bore. The vehicle's ignition system is the component that ignites the fuel air mixture inside the combustion chamber. When an ignition system fails, it can cause various symptoms such as stalling, rough engine under power, service engine light (check engine) and complete engine shut down. Be sure to keep your vehicle's engine and fuel system clean to assure the proper operation of your vehicle. The step by step instruction below is characteristic of today's ignition and air intake systems. Most vehicles today need a tune up every 35,000 to 65,000 miles depending on driving conditions. Before starting determine which tune up parts are needed. Inspect the particular system on your car or truck then purchase the appropriate parts to complete the job.
READ COMPLETELY BEFORE STARTING!

Step 1 - Identify Throttle Bore (air intake plate and bore)

Cleaned Throttle Body
Most vehicles have an air intake system that will become clogged with air contaminants that the air filter cannot keep out of the system. This condition is called "coking" and can cause stalling as well as variable idle condition and poor mileage. The throttle bore in this illustration has been cleaned for visual purposes. Usually the throttle bore and plate are coated with a dark light tar that needs to be cleaned with every tune up.

Step 2 - Cleaning the Throttle Bore and Throttle Plate (air intake plate and bore)

Most vehicles have a throttle cable that can be held open to help with the cleaning procedure. Open the throttle bore and with a cleaning towel and cleaner, (rubbing alcohol works well) continue cleaning until the throttle bore and plate are clean.

Step 3 - Identify Tune Up Components

Most vehicles have two kinds of ignition systems. The first is DIS (distributor less ignition system) and COS (coil over spark plug) no spark plug wires. If you can't identify which system you have, follow this link to get the right system for your car (car repair manuals). Confirm your vehicle to determine the tune up parts needed. A typical tune up includes spark plugs, air filter, fuel filter, spark plug wires, distributor cap and ignition rotor. You must determine which parts are needed before you start.

Step 4 - Remove Plug Wire Retainer Guide

Remove the spark plug wires retainer clip(s). These are important in keeping the plug wires separated and controlled to avoid any contact with undesirable components (exhaust manifold, drive belts etc). Clean and inspect the spark plug wire separators for reinstallation.

Step 5 - Remove Plug Wires

Remove the spark plug boot end and twist the boot to break the airtight seal created round the plug wire boot. Then gently pull the spark plug wire from the spark plug. Remove the plug wire from the coil terminal. It is important to change the spark plugs and wires ONE AT A TIME to make sure you don't get the wires mixed up.

Step 6 - Matching to Replace Plug Wires

Remove all plug wires from the packaging, straighten them out and organize the plug wires from largest to shortest. Match up spark plug wires by length and reinstall one at a time.

Step 7 - Remove Spark Plug

Next, remove debris from the spark plug hole, (canned air works best) then use a socket wrench and spark plug socket to loosen and remove spark plug (counter clockwise). Inspect spark plug for damage.

Step 8 - Replace Spark Plug

Remove the spark plug from the box or container and inspect the new plug for damage that could have occurred in shipping. A spark plug has a porcelain isolator that is fragile and can crack easily. Next inspect the spark plug gap using a spark plug gap checker. The "air gap" should be measured as per manufacturer specifications. Most plug gaps are between .035 and .045 thousands of an inch. This gap is important because it determines the amount of resistance used to "time" the system. An incorrect spark plug gap will result in poor running, low power, poor mileage and a check engine light notice. Reinstall the spark plug and install the new spark plug wire. Most of the time a spark plug will come "pre-set" and ready to install. Continue the process until all spark plugs and spark plug wires have been replaced. Be sure to use OE (original equipment) parts for your car to insure the proper performance from your vehicle. This tutorial has outlined a tune up on a gasoline power engine, four cylinder 1995 Saturn SL1. Most gasoline powered cars and trucks are similar.