Rough, Unstable, or Incorrect Idle, Stalling

Definition: The engine runs unevenly at idle. If bad enough, the car may shake. Also, the idle may vary in RPM (called "hunting"). Either condition may be bad enough to cause stalling. Engine idles at incorrect speed.
^ Perform careful visual check as described at start of Section B.
^ CHECK:
- Throttle linkage for sticking or binding.
- Ignition timing. See Emission Control
Information label.
- IAC system. See CHART C-2C.
- Generator output voltage. Repair if less than 9 or more than 16 volts.
- P/N switch circuit. See CHART C-1A, or use "SCAN" Tool.
- Injector balance. See CHART C-2A.
- PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve should snap back. If not, replace valve.
- Evaporative Emission Control System.
CHART C-3.
- Power Steering Pressure switch input. See
CHART C-1E or use "SCAN" tool.
- EGR valve: There should be no EGR at idle.
^ Run a cylinder compression check. See Section 6.
^ Inspect Oxygen 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 ECM will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
^ Check for fuel in pressure regulator hose. If present replace regulator assembly.
^ Check ignition system; wires, plugs, rotor, etc.
^ Disconnect MAF sensor and if condition is corrected replace sensor. "SCAN" tool should read about 6-8 grams per second at idle.