Conditions

Misfiring Randomly On Several Cylinders







Fault symptoms
CHECK ENGINE lamp is on or flashing. Engine running unevenly during misfiring. Possibly other diagnostic trouble codes present.

Conditions
The number of misfires required for the exhaust emissions to reach prohibited levels or damage the catalytic converter is stored in the control module memory in a matrix that is dependent on load and engine speed. A diagnostic trouble code will be generated if hhhhh misfires exceed the value in the matrix. Several cylinders misfiring.

Diagnostic help
The cause of the misfiring can be:
- Low fuel level in the tank This will be indicated by diagnostic trouble code P1416 also being generated
- fault in fuel system
low fuel pressure
EVAP canister purge valve continuously open
incorrect voltage from oxygen sensor 1
defective injectors
- fault in ignition system
incorrect spark plugs
incorrect ignition discharge module
- fault in basic engine
deficient compression
- fault in common components, pressure sensor, main relay, engine coolant temperature sensor

The cause of incorrectly detected misfiring, diagnostic trouble code P0300 without misfiring, can be:
control module pin 17 or 18 short-circuited to ground

Momentary misfiring can be read with the diagnostic tool
- Select "READ FUNCTIONS".
- Select "MISFIRING CYL 1".

The remaining cylinders can also be selected.

Checking the wiring harness. Intermittent faults may occur in connection with short circuits and open circuits. Jiggle the wiring harness at several points and in several directions to locate any problems in the wiring, including intermediate connectors. Observe the multimeter, scan tool or test lamp during the check.


WARNING
The electronic ignition system generates a tension of 40000 volts. This tension can be lethal for people with heart problems or pacemakers. The ignition system must therefore be treated with the greatest respect.


IMPORTANT
The ignition discharge module must be standing with the ignition coils facing down during the test so that the transformer oil will provide good insulation to the high tension part of the ignition coil