Rough Unstable Idle

SYMPTOM:
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 Exhaust Gas Recirculation system in "Testing
Flange gasket leaking, Procedures"
valve open (valve should
be closed at idle)


Positive Crankcase Ventilation
valve malfunction Check Positive Crankcase Ventilation system in "Testing
Procedures"


AT OPERATING TEMPERATURE


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


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