• Image by Flickr.com, courtesy of Reg Mckenna
  
  

Engine Requirements

• A gasoline engine needs three essential things to function: fuel, air and an electric spark. All of these must be present, in the correct proportion, and timed precisely for the engine to function correctly. Though engine diagnostics is as much an art as a science, you can do a number of things to understand why your engine is malfunctioning and what measures may be required to repair it.
  
  

Fuel Problems

• Without fuel, an engine will not run, and with too much fuel it will run inefficiently or not at all. The most common source of fuel system failure relate to the varnish and impurities that build up in the system over time. These impurities can clog filters, damage moving components and disrupt fuel flow through the tiny openings in fuel injectors and carburetor jets.
  
  

Airflow Problems

• Most air problems are due to an engine having too little of it, which richens the fuel mixture and causes engine stumble and bad fuel economy. Air filters need to be replaced at regular intervals, and performance air filters are a good buy for any car. The tiny idle-air bleeds that allow air into the engine during idle can stick or clog over time, leading to an engine that runs fine at speed but idles badly.
  
  

Spark Problems

• Possibly the most common of all engine-related problems, a bad spark can lead to an engine that idles badly, accelerates poorly and runs inconsistently or not at all. Often spark problems on modern engines are due to a flaw in one of the amplifier coils, a bad spark plug, bad grounding or a short in one of the wires. This type of failure can be recognized by an engine that idles poorly, hesitates upon acceleration, misfires at speed or sends a blue haze of unburnt fuel from the tailpipes when revved.
  
  

Electronic Problems

• Modern engines rely upon a vast array of sensors, relays and switches to run properly. Failure of any one of these switches can mimic the effects of any other sort of system failure, since there is very little built-in redundancy. Fortunately, new cars use an OBD-II systems diagnostic computer, which should alert the owner via a dashboard light if there is disruption anywhere in the system.