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Experiencing Engine Power Loss?

Updated on July 1, 2013

Diagnosing Engine Power Loss

If you're experiencing engine power loss, there are a lot of different potential causes. In order to properly diagnose your problem, there are some very important questions to ask:

  1. Was the power loss gradual?
  2. Was the power loss sudden?
  3. Did the check engine light come on?
  4. Is there white or black smoke coming out of the exhaust?
  5. Is there a scent of burning oil or unspent fuel in the exhaust?

If you have an answer, whether yes or no to all four of these questions, you'll be much closer to diagnosing the cause of your engine power loss. If you're not sure what the exhaust looks like or smells like, you might want to take a minute to check on it. Just make sure you don't stick your face in the exhaust. Get try and catch a scent from nearby.

Engine Loss of Power Causes

  • The Engine Power Loss was Gradual -- If this is the case with your engine, then the problem is most likely due to some form of clogging or improper gas/air fuel mixture. There are a number of places that a clog can occur and cause a slow and gradual loss of power. A dirty air filter, clogged fuel filter, clogged fuel pump, or clogged fuel injectors can all cause problems that will lead to loss of power and performance issues. In addition to this, if your Mass Air Flow Sensor (MAF) is faulty, you'll not be getting the proper air to gas ratio in your combustion chamber, which will also lead to loss of power and performance. Generally, with a gradual loss of power, the check engine light won't come on, unless things get to a certain point.
  • Engine Power Loss was Sudden -- If the power loss was sudden, it's almost always going to trigger the check engine light to come on. If the power loss was sudden and the check engine light didn't come on, odds are, the problem isn't with your engine. It could be with your throttle body or other component. there are a few different scenarios for why you'd be experiencing a sudden loss of power:
  1. Faulty Spark Plug -- A faulty spark plug will cause sudden loss of power because one of your cylinders is no longer firing. This means that fuel is going into the combustion chamber of a cylinder and is not being ignited. When this happens, you can generally smell unburnt fuel coming out of the tail pipe.
  2. Blown Head Gasket -- The head gasket is what keeps the coolant separate from the rest of the engine. When the gasket blows, coolant begins to leak into one or more cylinder. This can cause the spark plug to misfire because there's water and coolant in the fuel, which makes it inflammable. If your head gasket is blown, you should notice white smoke coming out of the tail pipe in the exhaust. This is the coolant and water being burned.
  3. Failing Seals -- There are seals in the engine which keep the oil from entering the combustion chamber, just like the head gasket does for the coolant. There are different kinds of seals, valve stem seals, piston rings, etc. If these seals begin to fail they'll allow oil to enter the combustion chamber of one or more cylinder, which can foul the spark plugs and keep them from firing. Generally, seals fail slowly. You've probably noticed recently that your car is beginning to consume oil. This is very common with older engines, which is why a lot of older engines use heavier weight oil, like SAE 30 or higher.
  4. Dirty or Broken Exhaust Gas Recirculation Valve -- The exhaust gas recirculation valve (EGR) reduces emissions in a car by recycling them back into the engine's intake stream. When this valve gets dirty or faulty, the check engine light will come on and you might notice the scent of gas when you start the car.
  5. Broken or Clogged Catalytic Converter -- The catalytic converter is another part of the exhaust system that recirculates exhaust back into the engine for reduced emissions. Catalytic converters should generally last as long as the car or truck, but sometimes they fail early and need to be replaced. When they fail, depending on the type of failure, the exhaust system will experience clogging, which will cause power loss and sometimes shaking.


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    • Benjimester profile image

      Benji Mester 4 years ago from San Diego, California


    • jabelufiroz profile image

      Firoz 4 years ago from India

      Useful article on Engine Power Loss. Voted up.