DME 7.8 DME 7.80 · During the system test for large lift, the valves remain at large lift,

DME 7.8 DME 7.80 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 1 valve on one cylinder is faulty. In order to guarantee safety during repairs, 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 sen- sor FR for this cylinder bank hardly changes the mixture at all given acceleration with wide-open throttle (FR at 1) and enriches the mix- ture in the opposite cylinder bank (FR > 1)⇒ see drawing below. Given a difference between FR1 and FR2 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 cylin- der banks. In this case, all flat-base tappets of the inlet valves must be replaced. A B 20 21 22 23 24 25 26 27 28 29 s 0-159 page 6 1555 P1353 p1353 Printed in Germany, 2000