For proper combustion in the car engine, the air-fuel mixture ratio is 14.7:1. In the mixture, the air portion is 14.7, and the fuel portion is 1. When the amount of fuel is more than the air that car faces running reach. On the opposite side, the fuel amount is less than the air in ratio; results car running lean. In this article, we will explain engine running rich causes and its troubleshooting.
Engine Control Unit (ECU) of the car is mainly responsible for maintaining the proper air-fuel ratio. Oxygen sensors, emission sensors, MAP sensors, MAF sensors, and fuel injectors also ensure the exact ratio to avoid running rich vs lean.
Engine Running Rich Causes and Symptoms
To get the exact 14.7: 1 ratio is rare in the car engine. It should be near to this ratio to get better performance. It will be a problem for you if the fuel amount is too much or less than the air portion. If you need to transfer fuel from one fuel tank to another, you should use a good fuel transfer pump.
Cars Run Rich Symptoms
We will describe here why car runs rough.
1. Check Car Engine Light
If you notice the check engine light signal on your dashboard, it means car engine is facing problems. You need to check with modern auto diagnostic tools. The error could P0172 showing on the device, means your exhaust pipe is bearing more amount unburnt gasoline.
MAP sensors control the air-fuel ratio and send the signal to the ECU of your car, which shows check engine light signal on dashboard.
2. Bad Smell
First of all, you will receive awful smell of rotten eggs from your exhaust pipe if your car engine running rich. The main reason for this smell is not burning the excess fuel in the combustion chamber. This unburnt extra gasoline comes out of the exhaust tailpipe. The catalytic converter is burning extra fumes but when the mixture is very rich, it cannot burn the unburnt gasoline.
3. Less Mileage
When you get less mileage of gasoline for your car regularly than the normal one, it is the symptoms of car running rich. That means your vehicle is burning more fuel than the requirement. But this case is not applicable for the winter season as you will get less mileage during cold time than average.
4. Low Engine Performance
When you notice poor engine performance in your car, it means the problem lies in an old spark plug, ineffective combustion chamber, or rich vs lean air-fuel mixture. If the spark plug and compression are perfect for your car, then the issues remain only with the air fuel mixture ratio.
5. More Carbon Monoxide Emission
Your car may release high carbon monoxide while running. It will fail the state emission state, and it is one of the engine running rich symptoms. Carbon monoxide is very harmful to human bodies. It can hamper you both physically and mentally.
6. Engine Rough Idling
The rich air-fuel mixture is liable for more vibrating of your car than usual. This car running rough is the symptoms of the run rich.
7. Lean Spark Plug
With car running rich, carbon deposits on the lower part of the spark plugs, which resulting in poor engine performance. It is one of the signs of extra unburnt gasoline in the exhaust.
Engine Running Rich Causes
The probable reasons:
a) Faulty oxygen sensor
Oxygen Sensors detect the fuel and air mixture ratio in the exhaust pipe. It sends the information to ECU and ECU adjusts this accordingly for getting the proper combustion ratio. But a faulty oxygen sensor cannot identify the problem which results in rich running.
b) Defective ECU
ECU controls the air-fuel mixture in the combustion chamber but the defective ECU cannot perform its job correctly. It is one of the causes of unburned gasoline in exhaust.
c) Imperfect MAF Sensor
MAF sensor controls the required air according to the amount of fuel. If your vehicle sensor is faulty, then your car engine will run rich.
d) Blocked air filter
Due to a clogged air filter or cold air intake, the engine receives less air than the required amount. The result is poor performance with extra unburnt fuel.
e) Faulty MAP Sensor
MAP sensor denotes the pressure inside the intake manifold and sends the signal to ECU. But due to faulty sensor, it cannot provide accurate data and the engine runs rich.
f) Congested Fuel Injectors
Due to one or two congested fuel injectors, engine does not a get proper fuel-air mixture ratio. Thus, the output is unburnt gasoline in the exhaust.
g) Ineffective Coolant Temperature Sensor
Coolant temperature sensor determines the engine temperature and sends report to ECU, which maintains the proper mixture ratio. The defective engine coolant temperature sensor cannot provide a clear signal, which results in rich running.
You should also know the probable reasons for car running lean:
a) Less fuel
b) Faulty regulator pump
c) Blocked EGR valve
d) Fewer fuel pressures
e) Leaking in compression
How to Fix Vehicle Running Rich Causes
1. Check Air Duct Flap
You will find a flap inside air duct which, acts as an open/ close valve. It opens partially just after starting the car engine and opens fully after engine warming up. If it does not perform according to that, you should fix it with a reliable mechanic.
2. Inspect Vacuum Lines and Hose pipes
If you notice loose vacuum lines and leaking radiator hose pipe, your car will run rich. The leaking can be identified by hissing sound. After detecting it, fix it immediately without any delay to improve your engine performance.
3. Clean MAF sensor
A faulty or dusty MAF sensor will give the wrong signal to ECU and get bad result from car engine. Clean it carefully, and follow the owner’s manual to get the instructions if are not confident enough. After cleaning, install it at the proper place. If you want to replace it, purchase the good quality sensors like Delphi MAF Sensor according to your vehicle.
4. Replace the Faulty Oxygen Sensor
Air duct flap, vacuum lines, MAF sensors are Okay and the problem is not solved yet. Then, the issue is with your problematic oxygen sensor. Replace it as soon as possible with the help of a technician and select the best sensors such as Denso Oxygen Sensor.
5. Change Spark Plugs
Defective spark plugs are not able to spark accurately. As a result, the mixture does not burn properly and found unburnt gasoline in the exhaust. The car will run rough if you do not change the worn-out spark plugs with the best one like NGK plugs.
Before doing any maintenance job, park your vehicle on a hard-flat surface, and wait until it becomes cool. Besides, you need to use car jack properly and ensure car stability to avoid any accident for doing any work under the car.
To Sum Up
You have already understood the engine running rich causes and its troubleshooting. So, follow the above instructions and solve the problem. Before changing any items, identify the problem first.
After changing any of the sensors or parts, drive your car a few minutes which will help adjust the proper air-fuel mixture ratios. You should also do your car’s regular maintenance to prevent rich or lean running.