P1319
P1319
Misfire, Emission Relevant
Function
To detect misfire, the drop in engine speed which results when no combustion occurs at one or more cylinders is evaluated.
A distinction is made between misfiring which is emission relevant and misfiring which is damaging to the three way catalytic converter (TWC).
The engine speed is measured with an inductive sensor that is located above the ring gear on the flywheel.
The ring gear is divided into three segments. For detection, the time between two segments is measured and the difference calculated. This difference is corrected by a mean value that is developed over several segments, to compensate for engine speed fluctuations caused by driving conditions. If the corrected value is above a specified threshold value which is dependent on engine speed and engine load, a misfire is detected.
Diagnosis conditions
A cycle of 1,000 crankshaft revolutions is evaluated (for misfire damaging to the TWC, 200 crankshaft revolutions). The misfire rates are compared with a threshold value. If the misfire rate is greater than the threshold value, a fault is recorded in the memory.
The Check Engine Malfunction Indicator Lamp (MIL) is switched on and stays on when the misfire rate lies above the threshold value which is 1.5 times over the FTP limit values during two consecutive driving cycles.
If the misfire rate may lead to permanent damage to the catalytic converter, the Check Engine MIL flashes. If this misfire rate is subsequently no longer reached, the MIL changes to a continuous light.
NOTE:
- 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.
- DTC P1585 can be read only with a scan tool. The Porsche System Tester 2 stores the fuel tank content (full or empty) under the ambient conditions.
- 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 an HOS2 signal fault ahead of the TWC is stored in memory, first correct this fault and then road test the vehicle.
P0300-P1585:
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 adaptation values of areas 1 and 2 are normal.
Remedy
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 adaptation values in area 1 differ in bank 1 and bank 2 (e.g. TRA=0.02/TRA2=0.27), the adaptation values for area 2 are generally normal.
Remedy
1. Reset camshaft control.
2. Road test vehicle. The adaptation values should be normal.
VarioCam does not switch over completely.
Cases have occurred in which the VarioCam of one bank was mechanically faulty. In these instances, the VarioCam had not switched 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 adaptation values of areas 1 and 2 are normal.
Remedy
1. Replace VarioCam.
2. Road test vehicle.
Wiring Diagram
Diagnosis Procedure
1 Read out mixture adaptation values TRA and FRA.
1. Connect Porsche System Tester 2.
2. Select vehicle type 996, DME, Actual values.
3. Select Area 1 (TRA), Area 2 (TRA2), Area 2 (FRA) and Area 2 (FRA2).
Display: e.g. Area 1 (TRA) 0.15
Area 1 (TRA2) 0.16
Area 2 (FRA) 1.05
Area 2 (FRA2) 1.04
-->Leaks in intake air system (ahead of intake air distributor). Affects both cylinder banks.
Display: e.g. Area 1 (TRA) 0.11
Area 1 (TRA2) 0.01
Area 2 (FRA) 1.01
Area 2 (FRA2) 1.01
-->Leaks in intake air system (after intake air distributor). Affects cylinders 1 - 3 only.
Display: e.g. Area 1 (TRA) -0.11
Area 1 (TRA2) -0.12
Area 2 (FRA) 1.11
Area 2 (FRA2) 1.12
-->Too little fuel in area 2 (e.g. insufficient supply from pump). Affects all cylinders. The considerable enrichment in area 2 also has an effect on area 1.
Area 1 is therefore adapted towards lean operation.
Display: e.g. Area 1 (TRA) 0.01
Area 1 (TRA2) -0.18
Area 2 (FRA) 1.01
Area 2 (FRA2) 1.16
-->Too little fuel in area 2, cylinders 4 - 6 (e. g. fuel injector fouled). The considerable enrichment in area 2 (cylinders 4 - 6) also has an effect on area 1 (cylinders 4 - 6).
2 Read out learning progress of sensor wheel adaptation.
1. Connect Porsche System Tester 2.
2. Select vehicle type 996, DME, Actual values.
3. Select Segment A, Segment B, Learning progress of sensor wheel adaptation.
When the values of segments A and B are around zero, e.g. 0.0003, adaptation is complete. The value of learning progress must then be smaller than 0.0005.
If the value of learning progress remains at 1.0000, the flywheel is defective.
If the values of segments A and B are also at 1.000, then adaptation has not yet been performed.
In this case, perform a test drive with three deceleration phases in the speed range from 3000 to 1400 rpm.
3 Check fuel pressure.
1. Undo and remove the closure cap of the fuel collection pipe test connection (A/F 13 mm).
2. Connect pressure gauge (special tool P 378a) to connecting line (special tool 9559) and connect to test connection.
3. Actuate fuel pump, either
- with Porsche System Tester 2
The fuel pump can be actuated with the Porsche System Tester 2 or by bridging the fuel pump relay.
or
- via fuel pump relay without tester
Disconnect the fuel pump relay from the central electrical system and bridge plug-in contacts 30 and 87 (identification 3 und 5 on central electrical system) with a fused shop-made cable. The fuel pump must now operate or deliver fuel.
4. Nominal test values
Stationary engine 3.8 ± 0.2 bar
Engine idling 3.3 ± 0.2 bar
NOTE: The seal or sealing ring in the brass closure cap is not exchangeable. It must therefore be used only once.
Tightening torque of new brass closure cap 2.5 ± 0.5 Nm.
4 Check volume supply of fuel pump.
Precondition:
Fuel filter and electrical supply OK.
1. Relieve pressure in fuel tank by opening tank cap.
2. Connect Porsche System Tester 2.
3. Remove complete air filter system.
4. Detach fuel return line (A/F 17 mm) from the engine compartment (left), taking care to hold it fast (A/F 17 mm). Collect residual fuel. Observe safety regulations.
5. Connect fuel hose (shop-made, approx. 1.5 meters long) to the fitting and hold in a measuring container.
6. Actuate fuel pump with the Porsche System Tester 2 and allow fuel to flow into the measuring container for 30 seconds.
Quantity supplied must be at least 850 cm3/30 s, i.e. after 30 seconds at least 850 cm3 of fuel must be in the measuring container.
NOTE: It is essential to observe safety regulations for handling fuel.
5 Check triggering of fuel injectors.
The fuel injectors can be individually suppressed with the Porsche System Tester 2 in the menu "Drive link active". The engine idle speed decreases if triggering is OK.
If no rpm decrease can be detected, check triggering as follows:
a. B+ supply
1. Remove connector of fuel injector to be checked.
2. Connect voltmeter to the valve plug contact, terminal 1, and ground using an auxiliary cable.
3. Switch on the ignition.
Display: battery voltage
If meter does not read battery voltage, check wiring according to wiring diagram for continuity or short circuit.
b Coil resistance of fuel injectors
1. Remove connector of fuel injector to be checked.
2. With ohmmeter, measure resistance between terminals of fuel injector.
Display: 11 - 13 ohms
c Injection output stage (negative supply)
1. Connect special tool V.A.G 1315 A/1 between fuel injector and connector.
2. Connect engine tester according to manufacturer s instructions. Connect cable for special input to special tool.
CAUTION: Tester cables must not be connected to ground.
3. Start the engine. For a perfectly working injector output stage, the following display must be shown at starting rpm.
NOTE: If the engine does not start, or if the idling speed drops, replace tester cable connected to special tool.