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.

^ See FLOW OF DIAGNOSIS.
^ Visually (physically) check:
- Vacuum hoses for splits, kinks or improper connections.
- Ignition wires for cracking, hardness, or proper connections, at both distributor cap and spark plugs.
^ Check throttle linkage for sticking or binding.
^ Check carburetor for flooding.
^ Check float level using external float gauge.
^ Check idle control operation.
^ Check engine idle speed, both base and ECM controlled. See Vehicle Emission Control Information label.
^ Check EGR system. There should be no EGR at idle.
^ If rough idle occurs hot, perform these additional checks:
- Check for proper PCV valve.
- Check PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve should snap back. If it does not, replace the valve.
- Check canister purge and bowl vent control system.
- Remove carbon with top engine cleaner. Follow instructions on can.
- Check for proper spark plug gap.
- Run a cylinder compression check.
^ Check ignition timing. See Vehicle Emission Control Information label.
^ Check for exhaust system restriction. See CHART B-1 RESTRICTED EXHAUST SYSTEM CHECK.