Stalls/Rough, Unstable or Incorrect Idle

SYMPTOM DESCRIPTION:
The engine runs unevenly at idle. If bad enough, the vehicle may shake. Also, the idle may vary in rpm (called "hunting"). Either condition may be severe enough to cause stalling. Engine idles at incorrect speed. Check the following systems and components.



COMPUTER INPUTS/OUTPUTS
^ ENGINE SPEED/REFERENCE SENSOR: Check for improperly positioned or damaged sensor. Check for damaged or missing teeth at the reference wheel.
^ IDLE VALVE:
^ AIR FLOW METER:
^ 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.
^ THROTTLE SWITCH: Improper adjustment.
^ COOLANT TEMPERATURE SENSOR:



FUEL
^ FUEL INJECTOR BALANCE TEST: Poor spray pattern, clogged or stuck.
^ FUEL PRESSURE: Check fuel pressure and output volume.



IGNITION
^ SECONDARY IGNITION SYSTEM:
^ DME CONTROL UNIT: DME final output stages.



EMISSIONS
^ EVAPORATIVE SYSTEM: Test purge valve and charcoal canister operation.
^ PCV VALVE: Test for proper operation. Refer to EMISSION CONTROLS for complete testing procedures.



ENGINE
^ VACUUM LEAKS: Test for vacuum leaks at intake system.
^ BATTERY: Cables and ground straps should be clean and secure.
^ CRANKCASE AIR LEAKS: Check at dip stick seal, oil filler cap, front and rear engine oil seals.
^ A/C refrigerant pressure too high, overcharge or faulty high pressure switch.
^ MOTOR MOUNTS:
^ CYLINDER COMPRESSION: