Table of content
27 October 2023 MAF sensor: what it is, symptoms of malfunction, and how to check it
The Mass Air Flow sensor is a relatively small component, but it is very important in engine management. Almost all modern petrol and diesel engines use the MAF sensor to calculate the optimum amount of fuel to inject. Let's take a closer look at how it works and how to spot the symptoms of a malfunction.
BOSCH Mass air flow sensor
Article number: 0 281 002 757
£ 80,75
price incl. 20% VAT, excl. delivery costs
BOSCH Mass air flow sensor
Article number: 0 281 006 487
£ 125,36
price incl. 20% VAT, excl. delivery costs
NTY Mass air flow sensor
Article number: EPP-MZ-003
£ 59,72
price incl. 20% VAT, excl. delivery costs
BOSCH Mass air flow sensor
Article number: 0 928 400 529
£ 164,43
price incl. 20% VAT, free delivery
-38%
Article number: 8ET 009 142-061
compared to
RRP
£ 128,20
£ 78,25
price incl. 20% VAT, excl. delivery costs
Function
The MAF sensor is a component of the engine's intake system and you will find it between the air filter box and the throttle valve on both petrol and diesel engines. It is mounted on an arm about 50 millimetres long so that it can be positioned centrally in the intake pipe. The flow sensor is connected to the car ECU module via a connector. A small seal prevents secondary air from entering the intake manifold. In addition to the air mass, the sensor also measures the temperature and pressure of the intake air. The control unit then uses these values to calculate the amount of fuel to be injected and the ignition timing. The air mass sensor in diesel engines also influences exhaust gas recirculation.
Symptoms of malfunction
The MAF sensor is not only essential for performance but for keeping pollutant emissions as low as possible as well. If it is faulty or dirty, it will not provide correct readings to the control unit resulting in the optimum quantity of fuel no longer being calculated. This can result in too much or too little fuel being injected into the engine's combustion chambers or intake causing the engine to run too "rich" or too "lean". Symptoms range from loss of power, irregular running, and fluctuating idle speed to misfiring and poor exhaust emissions, including black smoke. However, these and similar symptoms may have other causes, such as a fault in the turbocharger or ignition system.
Causes of a faulty sensor
In certain circumstances, the engine may switch to the emergency running programme if the air mass sensor is defective or heavily contaminated. The engine then runs at pre-set levels to protect itself and maintain the most acceptable exhaust emission levels but with significantly reduced power. The engine warning light comes on and a message is stored in the fault memory. However, the mass airflow sensor can also become defective sooner. When driving at high speeds in heavy rain, water can occasionally pass through the air filter. This can seriously affect the operation of the MAF. The sensor can also be damaged by the oil vapour that flows back from the crankcase ventilation system after the engine has been turned off. In addition, leaks in the intake tract can disable the sensor with sand or other particles.
Checking the air mass sensor
Reading the fault memory with a diagnostic tool is quite dependable – however, there may be no entry in the fault memory. If in doubt, the workshop has no other option but to replace the sensor, but this should only be done after a thorough analysis.
-60%
VDO Mass air flow sensor
Article number: 5WK96050Z
compared to
RRP
£ 344,78
£ 135,37
price incl. 20% VAT, free delivery
-28%
HELLA Mass air flow sensor
Article number: 8ET 009 142-131
compared to
RRP
£ 104,09
£ 74,42
price incl. 20% VAT, excl. delivery costs
DENSO Mass air flow sensor
Article number: DMA-0115
£ 115,04
price incl. 20% VAT, excl. delivery costs
BOSCH Mass air flow sensor
Article number: 0 986 280 700
£ 109,30
price incl. 20% VAT, excl. delivery costs
BOSCH Mass air flow sensor
Article number: 0 281 006 759
£ 72,37
price incl. 20% VAT, excl. delivery costs
Cleaning the air mass sensor
In some instances, cleaning the sensor may restore correct readings but be very careful as the sensor components are very delicate to touch. Modern airflow sensors use Torx screws to secure the sensor. On older models, the sensor is held in the housing by Phillips screws or simply by a connector. To clean the sensor, spray it with an electronic contact cleaner. When all parts are dry, reinstall the air mass sensor. It is worth checking the condition of the car's air filter and replacing it if necessary, and the air filter box and pipes should also be cleaned at this time.
Replacement cost
If it is necessary to install a new Corsa C MAF sensor, it is advisable to have a workshop replace this sensitive component as new MAF sensors sometimes require special tools. Fortunately, the sensor is easily accessible, so the cost of installation is relatively low. An experienced mechanic can usually complete the replacement within 15 minutes to an hour. It may be necessary to 'teach' the new MAF sensor in the control unit, i.e. to inform the electronics that a new MAF sensor is in use. If you choose to replace the MAF sensor yourself, make sure you use a high-quality product from a reputable manufacturer and proper parts.
The mass air flow sensor cost starts at about £30. It could be more problematic if you have an engine where the air mass sensor is integrated into the control unit. Repair costs can then run into four figures.
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