Vacuum Control Valve

NOTE: This Service Information supersedes MBNA 27/1, Jan. 1981, (modification of valve body M.Y. 1980, see attached work instruction) MBNA 27/3, Nov. 1981, and "Testing of Vacuum Control Valve" (Group 27, page 33 of 1983 Introduction Manual).

Since the beginning of Model Year 1981, a modified vacuum control valve was installed in production. Poor shift quality at partial throttle can be improved by adjusting this modified vacuum control valve.

If test value is found to be out of specified tolerance, start test by adjusting valve to an initial value of 145 mbar (Engines 617.91, 617.95), 200 mbar (Engine 616.91).

If the complaint is hard up-shifts, but the valve is found to be within specifications, the valve should be adjusted to the upper tolerance limit; in case of slipping during upshifts, adjust valve to lower limit.
Test Values (Millibar)


Vacuum
Control EGR
Engine Valve Valve

616.91 155-215 200-240

617.95 110-160 150-190
617.91
110-160 390-460
617.95* 320-350

*California version, 1980 model year.

FIGURE 1 - PUSH ROD CONFIGURATIONS:

Procedure

IMPORTANT: Push rod for vacuum valve should be checked for proper basic length and adjusted as required. Refer to Figure 1. At full throttle, a clearance of 0.5 mm (0.020 in.) should be maintained between the actuating lever and full throttle stop.


Individual adjustment of the push rod is no longer permissible..
1. Bring engine to normal operating temperature. Check automatic transmission fluid level and fluid condition. Check control pressure, adjust cable if necessary (617.95 engine only). Control cable has to return to idle rest position.

NOTE: A slight pre-load of up to 1 mm maximum is permissible.

FIGURE 2 - ENGINE 616, 617.912:

FIGURE 3 - ENGINE 617.95:

2. Pull vacuum line leading to transmission. Connect vacuum gauge using "T" or "Y" fitting (Figure 2 or 3).

FIGURE 4:

3. Check for presence of vacuum with engine idling. Disconnect actuating rod (5, Figure 4) and advance accelerator linkage to take up free travel, vacuum should now be present. Actuate lever to full load position and vacuum should drop. For any deviations, the vacuum system and primary vacuum lines should be checked first.


4. If vacuum was present in step 3 continue checking with engine idling. Place adjusting roller on vacuum valve stop pin and push valve lever against roller (arrow) (Figure 4).

Take up idle travel on throttle linkage and read vacuum on gauge. If value is within tolerance, but transmission shifts hard, adjust vacuum to upper limit. If slipping, adjust vacuum to lower limit. Adjust vacuum valve to 145 mbar (5 cylinder engines) and 200 mbar (4 cylinder engines) if value is out of tolerance.

FIGURE 5 - ENGINE 616.91, 617.91:

NOTE: Adjustment is only possible on valve with part number 123 070 00 46. Check part number on housing (arrow) (Figure 5).

If valve has part number 617 070 02 46 on actuating lever, it must be replaced with above valve.

FIGURE 6:

5. To adjust valve, remove cap (arrow) with pliers and hold lever against roller (Figure 6).

FIGURE 7:

6. Turn self-locking nut (arrow) until vacuum gauge shows correct value (Figure 7).

NOTE: Seal self-locking nut using commercially available Loctite.

7. Recheck vacuum as outlined in step 4. If no additional adjustment is required, replace cap on vacuum valve.

8. Check vacuum to EGR valve:

Engine 616.91, see 1982 Model Year Introduction Manual, page 32.

Engine 617.91, see 1981 Model Year Introduction Manual, page 127.

Engine 617.95, see 1983 Model Year Introduction Manual, page 28.

Engine 617.95 (California version, 1980 model year), see 1980 Model Year Introduction Manual, page 175.

If required, change orifice to next smaller or larger size.