Part 4
Figure:
WARNING: Tester cables must not be connected to ground.
NOTE: If the engine does not start, or if the idling speed drops, replace tester cable connected to special tool.
Perform system test for large lift
WARNING: Test is carried out while driving. Have a second person operate the Porsche System Tester 2.
During the system test for large lift, the valves remain at large lift, regardless of the type of driving. Faulty switching conditions can be detected by
rough running, just like with misfire detection. If a valve is not switched to large lift, the fault type 'over limit' is recorded.
Several cylinders may be stored as faulty, although only one valve on one cylinder is faulty.
In order to ensure that the fault is repaired, the flat-base tappets of the inlet valves of the entire cylinder bank should be replaced if a fault occurs.
A faulty flat-base tappet can be detected because the oxygen sensor F(R) for this cylinder bank hardly changes the mixture at all given acceleration
with wide-open throttle (F(R) at 1) and enriches the mixture in the opposite cylinder bank (F(R) > 1) - see drawing below. Given a difference
between F(R1) and F(R2) of more than 8 % during acceleration with wide-open throttle, a fault is certainly present.
If the difference is less than 4 %, 1 valve may be faulty on both cylinder banks. In this case, all flat-base tappets of the inlet valves must be replaced.