Fuel Injector – Deposits Can Build Up And Clog The Fuel Injector

Fuel Injector - Deposits Can Build Up And Clog The Fuel Injector
Fuel Injector - Deposits Can Build Up And Clog The Fuel Injector

A dirty or clogged fuel injector, can cause classic engine problems. For instance, lean misfire, rough idle, hesitation and loss of power.

So, it doesn’t take much of a restriction in a fuel injector, to lean out the air/fuel mixture. Gas is a mixture of many different hydrocarbons including, olefins which are heavy waxy compounds.

So, when the engine is off, there is no cooling airflow through the ports. And, no fuel flow through the fuel injector, to wash it away. As a result, heat bakes the olefins into, hard varnish deposits.

Consequently, these deposits can build up and clog the fuel injector. However, the formation of these deposits, is a normal result of engine operation.

Fuel Injector Deposits Comparison
Fuel Injector Deposits Comparison

So, detergents are added to gasoline, to help keep the injectors clean. But, if a vehicle is used mostly for short trips, the deposits may build up faster. Consequently, not letting the detergents wash them away.

On four-cylinder engines, the #2 and #3 injectors, are in the hottest location. And, tend to clog up faster than, the end injectors on, cylinders #1 and #4. Also, the same applies to the injectors in the middle cylinders, in six- and eight-cylinder engines.

As a result, the hotter the location, the more vulnerable the injector is, to get clogged from heat soak. However, throttle body injectors (TBI) are less vulnerable to heat soak. Because, of their location, high above the intake manifold plenum.

TBI System
TBI System

Fuel Injector Deposits And Failure Symptoms:

  • Starting issues
  • Poor idle
  • Failed emissions
  • Poor performance
  • Engine does not reach full (RPM)
  • Increased fuel consumption
  • Rough engine performance
  • Surging and bucking under various throttle loads
  • Smoke from the tailpipe
  • Not to mention Engine Knock or Detonation. Which can lead to fatal engine failure.
  • Pollution
  • Engine misfires

Cleaning Fuel Injectors


The benefits realized by injector cleaning obviously will vary, depending on the condition of the injectors. Injectors that are really dirty, should show a good improvement in performance. Either way, performance, fuel economy and emissions should all be better, after a cleaning.

Engine Codes

So, one of the obvious symptoms of clogged fuel injectors, is the lighting up of the “Check Engine” light. The engine codes usually associated with clogged injectors, can range from misfire codes to lean codes. Fault codes associated with clogged injectors, are the P0300 thru P0308. Consequently, indicates the engine controller is seeing an engine misfire.

Additional Signs To Watch For:

  • Restrictions
  • Turbo Troubles
  • Heat Soak
  • Also, Increase or Decrease in Long and Short-Term Fuel Trims
  • Not Enough Resistance
  • Longer Crank Times
  • Failed Balance Tests
  • Vehicle Won’t Start With Full Tank
  • Lack of Maintenance
Fuel Injector Firing
Fuel Injector Firing


So, high quality gasoline, has detergents designed to keep injectors clean. Yes, this implies that cheap gas, will take you down the fast road, to clogged injectors. Finally, the quality of the fuel you use, has a huge impact on fuel injector life.

Thank You !