Rough Unstable Idle

The engine runs unevenly. If bad enough, the car may shake. The engine idle may hunt or fluctuate in rpm and may be bad enough to stall.

POSSIBLE CAUSE ACTION


AT ALL TIMES
EGR malfunction, Check EGR system in "Testing
Flange gasket leaking, Procedures" in Emissions
valve open (valve should
be closed at idle)



Air management valves Check Air Injection system in
malfunctioning, no "Testing Procedures" in Emissions
air to ports while
in closed loop



PCV valve malfunction Check PCV system in "Testing
Procedures" in Emissions



COLD
Defective EFE valve or heater Check Early Fuel Evaporation system
in "Testing Procedures" in Emissions



AT OPERATING TEMPERATURE
Faulty canister purge Check Evaporative system in
and bowl vent valve "Testing Procedures" in Emissions



Restricted exhaust system Check Catalytic Converter system in
"Testing Procedure" in Emissions



Idle speed too low Check idle load compensator devices
in "Testing Procedures" and idle speed
in "Adjustment Procedure" in Emissions