Severe Engine Shudder During Acceleration
ENGINE SHUDDERS SEVERELY DURING ACCELERATIONPreconditions
^ DTCs in Motronic 4.3 ECM absent.
^ DTCs in AW 50-42 TCM absent.
^ Engine is hot.
^ Fault is permanent.
Fault Sources
^ Minor malfunction of spark plugs, ignition leads, rotor etc.
^ Moisture in spark plug wells.
^ Resistance in Mass Air Flow (MAF) Sensor.
TESTING PROCEDURE
Checking the Spark Plugs
^ Check if one of the spark plugs has thin brown lines or patches on the ceramic section beside the hexagonal nut.
If one of the spark plugs is defective:
- Replace all the spark plugs.
- Then continue with: Checking the distributor cap, rotor and ignition leads.
If the spark plugs are OK:
- Check the distributor cap, rotor and ignition leads.
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 Distributor Cap, Rotor and Ignition Leads
^ Ignition OFF.
^ Check the distributor cap, rotor and ignition leads for signs of damage, cracks and flashover.
^ Replace damaged components.
^ Continue with: Checking the MAF sensor's connector.
Checking the MAF Sensor's Connector
^ Clean and grease the MAF sensor's connector.
^ Check if the symptom remains.
If the car still runs jerkily:
- Connect the break-out box.
Connect the Break-Out Box
^ Connect the break-out box and check the ground connectors.
^ Connect the ECM.
^ Check all the signals to and from the ECM.