Symptoms of Fuel Injectors That Require Service

Symptoms of Fuel Injectors That Require Cleaning and Flow Testing Service


Dirty and clogged fuel injectors will have problems like fuel leak down, abnormal spray patterns, poor fuel atomization, and / or low fuel volume.  Clogged injectors can cause the following problems:

  • Excessive carbon deposits and build up on the injectors, valves, and pistons.
  • Failed emissions with excessive exhaust pollution.  Here, replacing a failed O2
    sensor will not fix the problem.
  • Computer Error Codes.  The computer will either read a cylinder misfire code, O2 sensor code, or an air fuel mixture problem.
  • Starting ProblemsThe engine is difficult to start hot or cold, or will not start at all.
  • Idling ProblemsRough and erratic idling.
  • Pinging and KnockingPinging due to pre ignition or worse, knocking due to detonation.  Detonation can lead to catastrophic engine damage.
  • Increased Fuel ConsumptionThe engine may have good performance and seem to run “fine”, but it is experiencing excessive fuel consumption.
  • Poor performance and a Loss of Power The car is just not performing like it should.  The vehicle may have low or high speed hesitation and surging.
  • Erratic Engine Performance with poor drivability.


Leaking Fuel Injectors that do not seal completely when turned “off” can cause the following problems:

  • Hard StartingHard starting Hot or cold due to fuel leak down with loss of  fuel pressure, and little or no initial starting fuel pressure.

  • Idling Problems

  • Increased Fuel Consumption Poor fuel economy

  • Exhaust Odor

  • Oil Thinning with gas, and cylinder bore “wash down”

  • Excessive Carbon and Varnish Buildup on valves and on the injector itself.

  • O2 Sensor Damage