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. Check the following systems and components.



COMPUTER INPUTS/OUTPUTS
^ 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 DME control unit will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
^ BATTERY VOLTAGE:
^ Digital Motor Electronic (DME) control unit grounds for being clean, tight, and in their proper location.
^ ENGINE SPEED/REFERENCE SENSOR: Missing or damaged teeth at the reference wheel, damaged sensor.
^ AIR FLOW METER: Sluggish flap movement



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



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



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



ENGINE
^ 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.