Rough, Unstable, or Incorrect Idle, Stalling

DEFINITION
Momentary lack of response as the accelerator is pushed down. Can occur at all vehicle speeds. Usually most severe when first trying to make the vehicle move, as from a stop sign. May cause engine to stall if severe enough.

PRELIMINARY CHECKS
^ Perform the careful visual / physical checks as described in Preliminary Checks. Refer to Diagnosis By Symptom / Preliminary Checks. Testing and Inspection

SENSOR CHECKS
^ Throttle Position (TP) sensor Check TP sensor for binding or sticking. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT).
^ MAP sensor - refer to Diagnostic Charts / C Charts / Chart C-1D Manifold Absolute Pressure (MAP) Output Check. Chart C-1D Manifold Absolute Pressure (MAP) Output Check
^ For sensors that share the 5 volt reference line for being skewed causing reference voltage to be pulled low.
^ 24x signal for being erratic, caused by a damaged or wobbling (out-of-round) reluctor wheel.

IGNITION SYSTEM CHECKS
^ Spark plugs for being fouled or for faulty spark plug wire routing.
^ Electronic ignition system ground, CKT 51.

FUEL SYSTEM CHECKS
^ Fuel pressure, use CHART A-7. Refer to Diagnostic Charts / A Charts / Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures
^ Contaminated fuel.
^ EVAP canister purge system for proper operation, use Chart C-3. Refer to Diagnostic Charts / C Charts / Chart C-3 EVAP Canister Purge Solenoid Check. Chart C-3 EVAP Canister Purge Solenoid Check
^ Fuel injectors. Perform fuel injector coil / balance test, use Chart C-2A. Refer to Diagnostic Charts / C Charts / Chart C-2A Fuel Injector Test Procedure. Chart C-2A Fuel Injector Balance Test

ADDITIONAL CHECKS
^ Service Bulletins for updates.
^ Exhaust Gas Recirculation (EGR) operation, use Chart C-7. Refer to Diagnostic Charts / C Charts / Chart C-7 EGR System Check. Chart C-7 EGR System Check
^ Engine thermostat functioning correctly and proper heat range.
^ Generator output voltage. Repair if less than 9 volts or more than 16 volts.