Hesitation/Sag/Stumble

Definition: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually most severe when first trying to make the vehicle move, as from a stop sign. May cause the vehicle to stall if severe enough.

POSSIBLE CAUSE ACTION
Choke valve remains open during cold engine operation Check choke operation and repair or adjust as needed. Choke Adjustments

Choke valve remains closed with engine at
normal operating temperatures Check operation and repair or adjust as needed. Choke Adjustments

Clogged enrichment jet Check operation and replace as needed.

Malfunctioning feedback solenoid valve Check operation and repair or replace as needed.

Malfunctioning vacuum switch Check operation and repair or replace as needed.

Malfunctioning engine coolant temperature sensor Check operation and repair or replace as needed.

Malfunctioning throttle position sensor Check operation and repair or replace as needed.

Malfunctioning engine speed sensor Check operation and repair or replace as needed.

Malfunctioning cold mixture heater relay control system Check operation and repair or replace as needed.

Broken, short circuited or incorrectly connected
harness connector Check operation and repair or replace as needed.

Malfunctioning air conditioner power relay control system Check operation and repair or replace as needed.

Weak or defective accelerator pump,
output to one side only may cause backfiring Check pump operation and replace or adjust as needed.

Metering rods, power valve rods,
or step-up rods sticking or binding Check and repair as needed.

Vacuum leak Inspect vacuum hoses for proper routing and damaged lines
Check intake manifold, carburetor base etc.

Heated air inlet system stuck at full hot or
full cold postion. Check operation and repair or replace as needed.

Incorrect float level Check and adjust as needed.

Inadequate fuel supply Check fuel pump output.

Excessive EGR rates due to sticking
or defective control system Check and repair as needed.

Carburetor transfer or idle system plugged Check and repair as needed.