Surges

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

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 fuel injection control unit will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
BATTERY VOLTAGE: See SPECIFICATIONS
Fuel injection control unit grounds for cleanliness, tight, and in their proper location.
CRANKSHAFT POSITION/SPEED SENSOR: damaged sensor.

FUEL
CHECK:
FUEL INJECTOR BALANCE TEST: Check for poor spray pattern, clogged, or stuck injector
FUEL CONTAMINATION: Check for water,diesel, or other contaminates in fuel
FUEL DELIVERY: Test fuel pressure and volume output.
TURBO: Bypass valve does not open, see FUEL SYSTEMS.
THROTTLE POSITION SENSOR: Incorrectly adjusted or faulty.

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.