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Here is a list of possible causes and what to do. Is the Check Engine Light indicating and was and trouble code retrieval performed? If not, get a free scan done at Autozone to see if any trouble codes are present.
ROUGH OR UNSTABLE IDLE
" If battery was recently disconnected, start and idle engine for 10 minutes, then recheck idle.
" If hunting, clean throttle body.
" Check Idle Air Control (IAC) motor.
" Check for vacuum leaks.
" Check PCV valve operation.
" Check for injector operation sound.
" Check fixed Speed Adjusting Screw (SAS).
" Using scan tool, check closed throttle position switch (if applicable), IAT sensor, BARO sensor, ECT sensor, EVAP purge solenoid, EGR solenoid, front and rear HO2Ss, power steering pressure switch, A/C switch, Park Neutral Position (PNP) switch and IAC motor position values.
" Check fuel pressure.
" Using scan tool, perform actuator tests for EGR solenoid and purge solenoid.
" Check ignition system.
" Check purge control system.
" Check compression pressure.
" Check for fuel contamination.
" Check coolant level
Friday, November 20th, 2009 AT 3:15 PM