If the surface is corroded or if the blades are damaged, replace the impeller

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyIntake Air Temperature Sensor Resistance Inspection
Remove the intake air temperature sensor (see Intake Air
Temperature Sensor Removal).
Suspend the sensor [A] in a container of machine oil so
that the heat-sensitive portion is submerged.
Suspend a thermometer [B] with the heat-sensitive portion
[C] located in almost the same depth with ...
Electrical Wiring
Wiring Inspection
Visually inspect the wiring for signs of burning, fraying,
etc.
If any wiring is poor, replace the damaged wiring.
Pull each connector [A] apart and inspect it for corrosion,
dirt, and damage.
If the connector is corroded or dirty, clean it carefully. If it
is da ...
DFI System Troubleshooting Guide
NOTE
This is not an exhaustive list, giving every possible cause for each
problem listed. It is meant
simply as a rough guide to assist the troubleshooting for some of the more
common difficulties in
DFI system.
The ECU may be involved in the DFI electrical and ignition system
tro ...