Clean fuel injectors are a must for peak engine performance, fuel economy and emissions. If the injectors are dirty and can't deliver their normal dose of fuel, then performance, fuel economy and emissions are all going to suffer. Dirty injectors can't flow as much fuel as clean ones, nor can they deliver the correct spray pattern that is so essential for clean, efficient combustion. The fuel feedback control system will compensate for the leaning effect once it is in closed loop, but it can't correct the underlying condition that is causing the problem.

The injectors need to be cleaned if an engine is experiencing any of the classic symptoms of dirty injectors, such as lean misfire, rough idle, hesitation and stumbling on light acceleration, a loss of power, and higher hydrocarbon (HC) and carbon monoxide (CO) emissions.

Lean misfire may also trigger a misfire code and turn on the Check Engine light on 1996 and newer vehicles with OBD II systems. The code often will be a P0300 random misfire code, or you may find one or more misfire codes for individual cylinders, depending on which injectors are most affected.

All Clogged Up

It doesn't take much of a restriction in an injector to lean out the fuel mixture. A restriction of only 8% to 10% in a single fuel injector can be enough to cause a misfire. When this occurs, unburned oxygen enters the exhaust and makes the O2 sensor read lean. On older multiport sy...