Uneven Idling

FAULT TRACING INFORMATION

Conditions
^ DTCs absent.
^ Engine warm.

Fault Sources
^ Defective spark plug.
^ Blocked/leaking injection valves.
^ Uneven compression.
^ Defective EGR valve.
^ Faulty sensor signals.
^ Damp in spark plug wells.
^ Badly adjusted camshafts.

TESTING PROCEDURE





Check Spark Plug
^ Check if any spark plug is lighter in color than the others.

If a spark plug is lighter-colored:
- Check injection valve.
If all spark plugs are the same color:
- Change all spark plugs.
- Continue with: Check fuel and residual pressure.

NOTE: It is very important that the correct spark plugs are used. Also check gaps of new plugs before fitting. Spark plug gap should be 0.7 - 0.8 mm.





Check Injection Valve
^ If any spark plug is lighter in color than the others, it means that cylinder is being starved of fuel.
^ Test with a new Injection valve. Also change all spark plugs.
^ Continue with: Check fuel and residual pressure.





Check Fuel and Residual Pressure
^ Ignition OFF.
^ Check fuel and residual pressure.

If residual pressure OK:
- Proceed to: Mechanical Check, section below.
If residual pressure not OK:
- Check that no injectors leak. Fix as necessary.





Mechanical Check
^ Carry out a compression test.

If compression OK:
- Proceed to: Check EGR, section below.
If compression uneven:
- Fix as necessary.





Check EGR
^ Let engine cool down (ECT less than 40°C (95°F)).
^ Ignition ON.
^ Read off values of engine and EGR temperature.
^ START engine and allow to idle.

EGR-temperature should increase more slowly than engine temperature.

If EGR temperature increases more slowly than ECT:
- Proceed to: Check Camshaft Adjustment, section below.
If EGR temperature increases more rapidly than ECT:
- Symptom indicates leaking EGR valve.
- Test with a new EGR-valve.





Check Camshaft Adjustment
^ Ignition OFF.
^ Check camshaft adjustment in relation to crankshaft.
^ Use gauge P/N 9995451, P/N 9995452 to check

If camshaft adjustment OK:
- Proceed to: Connect Breakout Box, section below.
If camshaft adjustment not OK:
- Adjust camshaft as necessary.





Connect Breakout Box
^ Connect breakout box and check control points.
^ Connect ECM.
^ Check all signals to and from ECM.