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Consumer Repair Guide
Tracking the Root Cause of Common Problems

It’s true that today’s models require less frequent maintenance and are more reliable on the road. Routine services of the past — such as tune-ups and air conditioning maintenance — will only be done a couple of times over the life of a car.

Let’s look at a common problem and consider the possible causes. This will help you understand how a “simple” repair can take several hours to diagnose.

What You Notice: Your car hesitates when you accelerate.

Possible causes your technician must check:

  • Low fuel pressure
  • Defective fuel pressure regulator
  • Restricted, clogged or dirty fuel injectors
  • Malfunction of the EGR valve position sensor
  • Defective coolant temperature sensor
  • Defective air charge temperature sensor
  • Defective throttle position sensor
  • Excessive exhaust back pressure
  • Carbon build-up in the combustion chamber (which causes detonation, thereby causing the knock sensor to retard ignition timing)
  • Faulty bearings in alternator, water pump, power steering pump or any other system (which creates a noise similar to detonation, thereby causing the timing to retard)
  • Use of incorrect octane fuel
  • Corrosion/erosion of spark plugs or spark plug wires
  • Faulty ground connection
  • Defective mass airflow sensor (MAF/MAP)
  • Faulty ignition module
  • Problem with the cam sensor
  • Problem with the crankshaft positioning sensor
  • Torque converter clutch

If your 1970 Mustang misfired, there were 10 likely causes for the problem. For this year’s model, there are 30 to 40 items to check. And that’s just a diagnostic start.

This is where the value of a quality technician becomes apparent. Diagnosing this complaint requires a repair strategy that will be developed based on the technician’s training and experience. He’ll consider all available information about the complaint, type of vehicle, service bulletins, and plan the investigation accordingly.