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
ECCS system Refer to On Board Diagnostics malfunction. in "Testing Procedures" in Emissions
to extract trouble codes.




EGR malfunction, Check EGR system in "Testing
flange gasket leaking or Procedures" in Emissions.
valve open.



Air temperature control system Check automatic temperature control system in
malfunctioning. "Testing Procedures" in Emissions.




Anti-backfire valve Check anti-backfire valve in
sticking open. "Testing Procedures" in Emissions.



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



AT OPERATING TEMPERATURE
ECCS system Refer to On Board Diagnostics malfunction. in "Testing Procedures" in Emissions
to extract trouble codes.



Faulty canister purge Check evaporative emission control system in
operation. "Testing Procedures" in Emissions.



Restricted exhaust system. Check Catalytic Converter system in
"Testing Procedures" in Emissions.



Idle speed too low. Check idle speed
in "Adjustment Procedures" in Emissions.