With Federal Emissions (Emissions Code D3)

UNEVEN IDLING

Preconditions
^ DTCs absent.
^ Engine is hot.

Fault Sources
^ Defective spark plugs.
^ Blocked \ leaking injectors.
^ Uneven compression.
^ Defective distributor cap, rotor or ignition leads.
^ Defective EGR valve.
^ Faulty sensor signals.
^ Moisture in spark plug wells.
^ Wrongly adjusted camshafts.

TESTING PROCEDURE





Checking the Spark Plugs
^ Check if one of the spark plugs is lighter in color than the others.

If one plug is lighter than the others:
- Check the injector.
If all the spark plugs are the same color:
- Replace all the spark plugs.
- Then continue with: Checking the Distributor Cap, Rotor and Ignition Leads section below.

NOTE: It is vital that the correct spark plugs used, see the parts catalogue for the P/N. Check also the spark gap of the new plugs before they are fitted. The gap should be 0.7 - 0.8 mm.





Checking the Injector
^ If one of the spark plugs is lighter in color than the other, this is a sign that this particular cylinder is receiving too little fuel.
^ Test with a new injector.
^ Replace all the spark plugs.
^ Then continue with: Check of residual pressure.

NOTE: It is vital that the correct spark plugs used, see the parts catalogue for the PIN. Check also the spark gap of the new plugs before they are fitted. The gap should be 0.7 - 0.8 mm.





Checking the Residual Pressure
^ Ignition OFF
^ Check the residual pressure.

If the residual pressure is OK:
- Check the distributor cap, rotor and ignition leads.
If the residual pressure is not OK:
- Indicates that an injector is leaking.
- Rectify as necessary.





Checking the Distributor Cap, Rotor and Ignition Leads
^ Check the distributor cap, rotor and ignition leads for signs of damage, flashover and oxidation.
^ Replace components suspected of being damaged or faulty.
^ Then continue with: Mechanical check.





Mechanical Check
^ Carry out a compression test.

If the compression is OK:
- Check the EGR.
If the compression is uneven:
- Rectify as necessary.





Checking the EGR
^ Let the engine cool down (engine coolant temperature below 40°C / 104°F).
^ Ignition ON.
^ Read off the Engine Coolant Temperature Sensor and EGR temperatures.
^ START the engine and let it run at idling speed.

EGR temperature should increase more slowly than engine coolant temperature.

If EGR temperature increases more slowly than engine coolant temperature:
- Check of camshaft settings.
If EGR temperature increases more quickly than engine coolant temperature:
- The symptom indicates a leaking EGR valve.
- Test with a new EGR valve.





Checking Camshaft Settings
^ Ignition OFF.
^ Check the camshaft settings in relation to the crankshaft.
^ Use gauge P/N 9995451, 9995452 to check.

If the camshaft settings are OK:
- Continue to: Connection of break-out box.
If camshaft settings are not OK:
- Adjust the camshafts as necessary.





Connect the Break-Out Box
^ Connect the break-out box and check the ground connectors.
^ Connect the ECM.
^ Check all signals to and from the ECM.