What are the P0172 & P0175 fault codes? Is rich mix failure possible? What can be done to fix P0172 or P0175 fault codes What are the causes and symptoms of poor mix failure?
For low fuel consumption and emissions, the engine computer (PCM), tries to maintain a 14.7/1 ratio in the air-fuel mixture. To put it another way, 14.7 units are required for a gasoline engine to burn 1 unit (or fuel) in the combustion chamber. Rich Mixture is when the ratio of air and fuel mixture is less than 14.7/1 (12/1). A rich fuel mixture may produce more power (upto a point), but it also has a higher fuel consumption and emission. A “Lean Mixture” in a vehicle is formed if the fuel/air ratio exceeds 14.7/1 (16/1). Although a poor mixture may reduce fuel consumption, it can also cause engine misfires and high emissions.
The PCM monitors the ratio of air/fuel with oxygen sensors located in the exhaust manifold. The oxygen sensor measures the vehicle’s mixture of fuel and air. The O2 sensor will send a low voltage signal to inform the computer that the engine has run lean. This means there is too much fuel and too little air. The O2 sensor sends a higher voltage signal (informing the computer that the engine has too much fuel) to inform it that the fuel supply is being cut. The computer will adjust the fuel delivery according to its needs.
When a cold engine starts, it takes about 10-30 seconds for the oxygen sensors in order to warm up. The fuel mixture is maintained at a preset level during this time. The PCM adjusts the fuel mixture when the coolant temperature and oxygen sensors reach the desired consistency.
When the engine is turned off, the PCM retains fuel trim values. The vehicle can then pick up the place it left off when it is started over again. The fuel trim values can be cleared by disengaging the battery or clearing the PCM memory using a scan tool. The engine computer will then start to calculate the fuel consumption of the vehicle starting at zero.
Possible causes of rich mixture failure
- – Defective or dirty Air Flow Sensor (MAF).
- – Fuel injector clogged or leaking
- – Defective fuel pressure regulator
- – Defective fuel pump
- – Fuel pipe bending and crushing can cause restrictions
- – Defective Water Temperature Sensor
- – A defective thermostat
- – A clogged and dirty air filter, or air intake system restrictions
- – Exhaust restrictions (clogged exhaust/muffler, damaged tailpipe)
- – A defective O2 sensor that reads “Rich” when the output voltage has been reduced.
- – Vacuum leaks
- – Incorrect fuel pressure
- – Worn spark plugs
- – It is possible that the ECU needs to be reprogrammed.
Rich Mixture Harms
- – An excessively rich mixture causes the catalytic convert to do more filtration. This decreases the life span of the catalytic convert.
- You will be able to enrich the gas stations as the vehicle’s fuel consumption will rise.
- The engine will work harder if the air/fuel ratio is incorrect. This can reduce the engine’s lifespan.
- – Vehicle emissions will rise and pollute the environment more. Exhaust starts to emit black smoke.
- – It is possible that even though the vehicle displays some symptoms, such as misfires, the driver will not notice any issues with it.
Possible Solutions
- – Replace any damaged or worn vacuum and PCV hoses.
- – Look for any blockages in your air intake system.
- – Cleanse the MAF sensor. This task can be done with special electronic cleaner sprays. Make sure to not damage the MAF sensor.
- – Inspect the fuel pipes for cracks or leaks, crushing, breaking, or bending.
- – Check the fuel pressure within the fuel rail.
- – Inspect the fuel injectors. The fuel injectors could be dirty. You can clean the injector using cleaning sprays. Experts may also be available for assistance. Replace if defective.
- – Before the oxygen sensor, check for any exhaust leakage. Although it is unlikely to cause the problem, it is possible.
- – Inspect the oxygen sensor.
Check that the cooling system of your vehicle is functioning properly. The engine will always run full if the cooling system is not working properly. This is because the engine computer will send more fuel to warm a cold engine. The vehicle will not heat up if the water temperature sensor or thermostat are damaged.
