Surges at Steady Speed or While Cruising

SYMPTOM DESCRIPTION:

Engine power variation, under steady throttle or cruise. Feels like the vehicle speeds up and slows down, with no change in the accelerator pedal.




SYSTEM OR COMPONENT TO CHECK ACTION

COMPUTER INPUTS/OUTPUTS CHECK: ^ OXYGEN SENSOR (O2) - Inspect sensor for
silicon contamination from fuel, or use of
improper RTV sealant.
The sensor will have a white, powdery coating,
and will result in a high but false signal
voltage (rich exhaust indication). The electronic control
unit will then reduce the amount of fuel delivered
to the engine, causing a severe driveability
problem.
^ BATTERY VOLTAGE:
^ electronic control unit grounds for being clean,
tight, and in their proper location.
^ ENGINE SPEED/REFERENCE SENSOR: Damaged
sensor.
^ AIR FLOW METER: Sluggish flap movement.




FUEL CHECK: ^ FUEL INJECTOR BALANCE TEST:
Check for poor spray pattern, clogged, or stuck injector
^ FUEL DELIVERY: Test fuel pressure and
volume output.



IGNITION CHECK: ^ Proper ignition voltage output
^ Spark plugs, wet plugs, cracks, wear, improper
gap, burned electrodes or heavy deposits.





EMISSIONS CHECK: ^ EVAPORATIVE SYSTEM:
Extremely high ambient temperatures
can cause excessive amounts of purge vapors
to enter the intake system.




ENGINE CHECK: ^ VACUUM LEAKS AT INTAKE SYSTEM:
Vacuum lines and gaskets for leaks.
^ CRANKCASE AIR LEAKS: Check for leaks at
dip stick seal, oil filler cap, front
and rear engine oil seals
^ AUTO TRANSMISSION OPERATION: Erratic
(up or down) shifts
NOTE: ^ Be sure driver understands
Torque Converter Clutch and A/C
compressor operation in owner's manual.
^ A/C REFRIGERANT CHARGE: Over charged
system or defective high pressure
cutout switch.