- When the fuel tank is driven to empty, misfiring can occur. For this reason the fuel level in the tank is also stored in the memory when
misfiring occurs. If the tank was empty, there was probably no fault. Erase fault memory and road test vehicle.
- In the event of a short circuit to B+ or ground of the oxygen sensors ahead of the TWC, the mixture becomes too lean or too rich. This can
cause misfiring. If, in addition, an oxygen sensor signal fault ahead of the TWC is stored in memory, first correct this fault and then road test
P0300 - P0306
NOTE: If the battery was disconnected, at least range 1 must be adapted before troubleshooting is carried out.
Possible Mechanical Causes Of Faults
Valve lifter chattering.
This is caused by dirt in the valve lifter.
When the Check Engine MIL lights up, a chattering valve lifter may also occur for a certain time. The DME control module registers (sporadic)
misfiring at one or more cylinders. The mixture adaptation values are normal.
1. Remove lifter bores, check for damage and blow out oil passages.
2. Replace all valve lifters (engine installed).
3. During the test drive, listen for valve lifter noises.
Camshaft control badly adjusted.
The camshaft control has changed. No chattering noises occur. The DME control unit indicates misfiring for the entire cylinder bank 1 or 2. The
mixture adaptation values in the idle speed range differ in bank 1 and bank 2, the mixture adaptation values in the upper and lower load ranges are
Carry out raw emission measurement:
- Reset mixture adaptation values (disconnect battery)
- Disconnect oxygen sensors
If the difference between bank 1 and bank 2 is greater than approx. 0.8 %, then
1. Reset camshaft control.
2. Road test vehicle. The mixture adaptation values must be normal.
VarioCam does not switch over completely.
The VarioCam does not switch over completely from power to torque valve timing.
An indication of this problem is misfiring detected by the DME control module in the range of 1200 - 1500 rpm occurring in an entire bank.
The mixture adaptation values are normal.
1. Replace VarioCam.
2. Road test vehicle.
Other possible fault causes
- worn camshafts
- leaking valves
- faulty piston rings
If opposing cylinders have misfiring, the cause could be the sensor wheel.