Rough Unstable Idle

The engine runs unevenly. In severe cases, the car may actually 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"
valve open (valve should
be closed at idle)




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




PCV valve malfunction Check PCV system in "Testing
Procedures"



AT OPERATING TEMPERATURE
Faulty canister purge Check Evaporative system in
valve "Testing Procedures"



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