Car Starts But Wont Stay Running (Reasons and How to Fix It)

“My car starts but wont stay running for long. What should I do? You probably have found yourself in such a situation. There are times when a vehicle runs for seconds and then shuts off by itself, or it can die while driving and won’t start. This may be a result of different failures in the parts of the vehicle. Identifying the exact possibility of this failure may be challenging when you do not understand the car systems. Many people have reported having similar failures such as “my 2000 BMW starts but won’t stay running” or “my car starts then die unless I give it gas.” This article is here to give solutions to complaints and answer all the questions related to these kinds of problems.

What the Reasons Car Starts But Won’t Stay Running:

As we stated, this failure involves many parts. You need to do several checks and fixes to know the exact causes of the faults and how to deal with them the right way.

Ignition System Problems: The 3 core elements for the car to start and run are fuel, spark, and air. If these three elements are available in the correct ratio, then the car will run smoothly and will not stop. If one of the three elements fails to decrease or increases slightly, the ratio changes and the car will not have a smooth running. After a while, it will shut off due to a bad spark or since the fuel support is not enough to sustain the engine and keep it running. This is what causes the car to start and then die when cold.

Bad Canister Vent Valve: The canister vent valve is part of the (EVAP) which is the evaporative emission control system. Its role is to route the vapors produced from the fuel and get them back to the canister and from the canister to the intake manifold. It then goes to the combustion chambers and gets fired by the spark plugs. The benefit of this system is to reduce fuel consumption. If this system fails, the car becomes unstable when idle and it turns off immediately after starting up.

PCV Valve Failure: PCV (positive crankcase ventilation) valve is a valve designed to purge blow-by gases in the engine from the heating of the oil. It is resent to the intake manifold for lubricating and re-burning purposes. The PCV systems use a very tiny valve to get this job done. This valve goes open when purging the overloaded pressure. When this valve is defected and remains open, it results in an overflow of air streams into the intake manifold when idle or accelerated, causing the car to stall.

TPS Fault: TPS (throttle position sensor), is the sensor responsible for sending the throttle position to the ECU (engine control module). The importance of this signal is that ECU calculates the quantity of fuel to be provided to injectors to keep the right ratio between air and fuel in the mixture. When the throttle position sends the wrong signal to the ECU the fuel quantity delivered to the injector’s rail will be wrong; thus, the car may stall on idle. And you will notice that car starts but won’t stay running unless the foot is on gas.

ECT Sensor: This component helps the engine to protect itself and prevent its performance from getting by the engine temperature. The ECT (Engine Coolant Temperature) sensor is here to send information about the engine’s temperature to the ECU to adjust the mixture of air and fuel. When the ECT sensor is faulty, it sends wrong or false information about the temperature of the mixture, making it hard for the ECU to provide the right fuel quantity. The combustion will not be right, and this will cause roughness while driving the car and sometimes lead to stalling. The worst side of this kind of failure is that if the engine overheats the fans do not work at maximum speeds since they don’t have signals that the temperature is too high.

EGR Valve Defect: The EGR (Exhaust Gas Recirculation) is a system that recirculates part of exhaust gases back into the engine to reduce the temperature of the combustion chamber by getting this small portion of the exhaust gas back into the intake manifold. It is usual for the EGR valve passages to get stuck and blocked by the carbon build-ups. This prevents the valve from closing, thus making an extra air stream inside the engine that will cause stall and instability while idle.

Read: How to Clean Your EGR Valve?

Catalytic Converter: The catalytic converter’s role in the car is to revise, correct, and evaluate the work of the engine. It makes sure that the combustion is running well. The catalytic converter is usually attached to an oxygen sensor. The role of this sensor is to analyze the exhaust coming out of the combustion chambers and detect the percentage of oxygen in it. Depending on this info it corrects the air to fuel mixture to make successful combustion. The combustion is just balanced, and it’s neither lean nor rich. Therefore when the catalytic converter has a defect or is made of low quality, the sensor will not give accurate readings, and the air to fuel mixture will be affected negatively.

Wrong Injector Pulses: If you always feel that a car starts then sputters and dies, it could be as a result of wrong injector pulses. As we talked about before that to have successful combustion, three elements must be provided in specific quantities. They include the spark through the spark plugs, air going into the engine through air ducts and passing by the air filter, and finally the fuel supplied into the engine by injectors. Injectors perform this process via pulses. When the ECU gives a signal to the injector, it magnetizes the plunger and sprays fuel into the intake manifold or in the cylinder directly in some systems which are the GDI. Therefore, if these injectors are failing to give the right pulses, giving pulses at the wrong timing, or have a defect like over bleeding fuel, it prevents perfect combustion of this unsmooth running.

CMP\CKP: It is either called Camshaft Position Sensor or Crankshaft Position Sensor. You will never have a balanced performance out of your car if you have a defective camshaft position sensor or crankshaft position sensor. The work of the sensors is defining the timing and the spot of the crankshaft and camshaft. They also define the degree to of the valve opens to provide the air and fuel mixture to the combustion chambers. All this info is sent to the ECU for processing and analysis. It then decides on when to ignite the spark and when to spray the specific quantity of fuel. It also decides on the depth of the valve opening to be adjusted depending on the information.

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How to Fix the Problems

To fix any of the above problems, the first thing is to have the right diagnostic using the correct tools. It will take you time and cost trying to find the fault in traditional ways. Many of the defects mentioned above and failures cause the (MIL) diagnostics lamp to go ON. First, attach the diagnostic device compatible with your car model, and then start scanning the fault codes. Here we are going through some of the most popular fault codes that define the error precisely:

P0300 – P0312: These codes define an error in the ignition system such as misfires. In this situation, you should start by changing spark plugs and then check again if the code will still appear. If it re-appears, the problem could be in the ignition coil or ignition coil cables. After checking the spark plugs remember to connect the Spark plug wire correctly to avoid any other defects.

P0335 – P0339: These errors usually represent a problem in the crankshaft sensor, which may vary from mis-programmed or false calibration sensors. In this case, get to the programming section and check the programming tools of the vehicle. Calibrate the sensor in this section. If errors are still there after re-programming, then you need to change the defective sensor depending on the code.

P0340 – P0349: Misaligned Camshaft sensor may fail the car operation resulting in stalling and stopping once starting. As stated in the crankshaft sensor, the same applies here.

P0400 – P0409: If an EGR error is found on the diagnostic platform, the first thing we need to disassemble is the EGR valve to clean its inside. You also need to check the sealing of the EGR. EGR should be cleaned in periodic maintenance to avoid faults and errors.

P0500 – P0511: This error group represents errors in the throttle body and sensors assembled in it. This includes an idle speed sensor that is responsible for ensuring a minimum amount of air gets through the throttle body to keep the engine running smoothly. If carbon build-ups block this air passage, the car will stall in an idle state, or the car starts but dies after a few seconds. You have to keep your foot on the gas to keep the vehicle running. In this case, you are required to disassemble the sensors out of the throttle body. Using a throttle cleaner, spray on it to dissolve the stains and carbon it. You can then get it back into the car. In some models, the throttle body needs to be re-program after installation. Always check the shop manual before disassembling.

P0520 – P0523: This group of errors is related to the PCV system. If you find one of these errors, locate the PCV in your engine (usually in the cylinder head and connected with a hose to the throttle body). If you find that the valve is blocked, try to clean it. It is always preferable to change it since it is very cheap and easy to install. Note that failing to change the PCV valve may lead to adverse consequences such as the Head gasket Blown due to an overload pressure inside the engine.

P0087 – P0094: These errors are related mainly to the defects in the injection systems. From the error code, you can define which injector has the problem. After you know the defective injector, you can either clean it using the ultrasonic device or just change it. However, before changing the injector, inspect to see if the wiring harness is 100 % in a good state.

Final Words:

If your car starts then dies after a few minutes, or even seconds, you can be sure to find the reason for the fault in this article. The secret to ending this problem from the root has a proper diagnosis. I, therefore, suggest that you use the car-supported diagnostic tool to get full sensors scan, complete programming, and calibrating abilities. Finally, if you feel so confused about the problem, it is always a good idea to ask an expert for a solution. You will save time, and money, and get your car recovered easily and hassle-free.