A Peugeot 207 may shake, hesitate or suddenly start using more fuel. This often points to a faulty lambda sensor or dirty injectors. These two components work closely with the engine computer and determine fuel combustion. If this cooperation goes wrong, you will notice it straight away in the performance and fuel consumption of your Peugeot 207. Curious about the symptoms and how to tackle the problem? Read on.
What is the role of the lambda sensor in the Peugeot 207?
The lambda sensor, also known as an oxygen sensor or O2 sensor, measures the amount of oxygen in the exhaust gases. Based on this measurement, the engine computer determines how much fuel should be injected. If the sensor does not function properly, there will be too much or too little fuel in the mixture. This has an immediate effect on the fuel consumption and emissions of your Peugeot 207.
What are the symptoms of a faulty lambda sensor in the Peugeot 207?
A faulty lambda sensor shows itself in several ways. If you recognise any of the signs below, it is wise to have the sensor tested.
- Uneven engine running and vibrations, especially noticeable at low revs
- A noticeable increase in fuel consumption due to an inefficient mixture
- Black or white smoke from the exhaust due to an incorrect mixture
- Starting problems with a cold engine, where the engine computer tries to compensate
Some owners replace the lambda sensor. However, this does not always fully solve the problem. In that case, the serpentine or the ignition coil may be the real cause. The serpentine is a hose in the exhaust. A blocked serpentine puts extra strain on the ignition coil. This mimics a lambda sensor fault. It is therefore wise to include these components in the diagnosis before replacing only the sensor.
Testing the lambda sensor: what should you look for?
When testing the sensor with a measuring device (multimeter), it is important to check the fuse first. A blown fuse can make the heater resistance in the sensor impossible to measure. This may lead you to draw the wrong conclusion about the condition of the lambda sensor. When replacing it, the connector on the new sensor should be briefly treated against corrosion so that it lasts longer.
Why is my Peugeot 207 running erratically?
Erratic running in the Peugeot 207 is often linked to dirty or faulty injectors. This applies to both petrol engines, such as the 1.4 and 1.6, and the HDi diesel (high-pressure injection system). In petrol engines, it is about disrupted mixture formation. In diesel engines, it is about fluctuations in rail pressure (fuel pressure in the supply rail), the pressure at which fuel is sent to the injectors.
Recognisable symptoms of injector faults are:
- Jerking or hesitation while driving
- Starting problems or the engine suddenly cutting out, especially with the HDi diesel
- Reduced pulling power and a sluggish response to the accelerator pedal
In the HDi diesel, a faulty rail pressure sensor is often the cause of starting problems. Low or unstable rail pressure means that the injectors cannot inject consistently. This is immediately noticeable while driving.
How do I clean injectors in the Peugeot 207?
Dirty injectors do not always need replacing straight away. Follow these steps as an initial check before considering larger repairs.
- First check the rail pressure on the HDi diesel, as low pressure is more often an indication of a sensor problem than a faulty injector.
- If in doubt, have a diagnosis carried out with equipment that measures the pulse width (duration of the injection signal) of the injector. A value of around 25 milliseconds instead of the usual 16 milliseconds stands out. This points to an engine problem or poor valve sealing.
- Consider professional injector cleaning if the engine hesitates without any clear fault codes.
- Only replace the injector itself if cleaning and sensor checks do not improve matters.
If you replace related sensors, such as the sensor on the crankshaft (crankshaft sensor) on the 1.4 and 1.6 HDi, use the original reference 96 374 669 80. This prevents starting and running problems from returning after replacement.
Lambda sensor and injector: where should you start looking?
If you are experiencing rough running or higher fuel consumption, it is wise not to replace the most expensive parts straight away. Start with the cheaper and more accessible checks.
- First check the serpentine and ignition coil in the exhaust before replacing the lambda sensor
- Test the fuse and the resistance of the sensor with a multimeter
- On the HDi diesel, measure the rail pressure and the injector pulse width (see previous explanation)
- When replacing sensors, always use the correct original reference
This order prevents unnecessary costs and helps you find the cause of the fault more quickly.
‘This helps you identify more quickly whether a complaint is known as a typical problem for your model, and know exactly which checks you can carry out yourself first before going to the garage.’
Want to know more about car problems and maintenance
Unsure about a starting problem, a fault code or another issue with your Peugeot 207 or another model? On Carnews you will find focused articles on, among other things, diesel particulate filter problems on HDi engines, electrical faults and common dashboard warning messages. That way, you can more quickly recognise whether a complaint is known as a typical issue for your model, and you will know exactly which checks you can carry out yourself first before going to the garage.
Frequently asked questions
Common symptoms of a faulty lambda sensor in a Peugeot 207 are uneven engine running and vibrations, a clearly higher fuel consumption, smoke or unusual exhaust gases and sometimes starting problems (especially with a cold engine). With faulty injectors, jerking or “hesitation” while driving, loss of power and poor throttle response often occur, and in more severe cases starting problems or the engine cutting out unexpectedly, especially with HDI diesels.
A faulty lambda sensor can cause the engine management to choose a mixture that is too rich or too lean, making the engine run roughly, reducing power and noticeably increasing fuel consumption. Faulty or dirty injectors cause poor or uneven fuel atomisation, which results in jerking, loss of power and sometimes poor starting. In both cases the car may smoke more and accelerate less smoothly. It is therefore advisable to have the car diagnosed quickly when these symptoms appear to prevent further damage and higher fuel consumption.
A car enthusiast can start by reading the engine management system with an OBD2 scanner to see whether there are any fault codes specifically referring to the lambda sensor (O2 sensor) or a particular injector. They can then visually check the wiring looms, connectors and fuses for the lambda sensor and injectors for damage, corrosion or poor connections. They can also assess engine behaviour (rough idling, hesitation, vibrations) together with higher fuel consumption and exhaust smoke to determine whether it is more likely a mixture/lambda problem or a single misfiring cylinder (injector). Finally, using measuring equipment (a multimeter or live data in the OBD app), they can check whether the lambda sensor is producing changing voltages and whether the fuel trims and rail pressure remain within normal values, which provides clues to a poorly working sensor or injector.
The primary causes of lambda sensor faults in the Peugeot 207 are contamination or ageing of the sensor, exhaust problems such as a blocked section of the exhaust (serpentine/silencer) and electrical problems such as poor wiring or fuses, causing the sensor to give incorrect readings. This disrupts the mixture control system, leading to unstable engine running, increased consumption and emissions problems. Injector faults are mainly caused by contamination or mechanical wear of the injectors themselves and problems in the high-pressure system (such as rail pressure or rail pressure sensor issues, especially on HDi diesels). These causes lead to incorrect or insufficient fuel atomisation, which shows itself in jerking, starting problems, loss of power and sometimes engine stalling.
Always use good-quality fuel and change the oil and oil filter according to the service schedule, so that combustion residues and soot build-up around the lambda sensor and injectors are limited. Let the engine reach operating temperature properly and avoid lots of short journeys, as these cause extra condensation, soot and enrichment that contaminate the lambda sensor and injectors. Periodically use a suitable injector-cleaning additive in the fuel and replace the fuel filter in good time to prevent blockages and poor atomisation. During servicing, have the exhaust and the electrical connectors of the lambda sensor and injectors checked and, if necessary, treated against corrosion.
