Rough, Unstable, or Incorrect Idle, Stalling

Definition: 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 bad enough to cause stalling. Engine idles at incorrect speed.

^ Perform "Diagnostic Circuit Check - Calif".

^ Perform "System Performance Check - Calif".

^ Visual (Physical) Check:

- Vacuum hoses for splits, kinks and proper connections as shown on Vehicle Emission Control Information label.

- 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 gage.

^ Check engine idle speed. See Vehicle Emission Control Information label.


^ Check EGR System. See Chart C-7. There should be no EGR at idle.

^ If rough idle occurs hot, perform these additional checks:

- Check PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve should snap back. If not, replace 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.