Engine Shakes at Idle

07.3-85011 Shaking of Engine at Idle Engine 116.96, 117.96 Revised 1/86 1/85
with electronic idle
speed control





In order to differentiate if the electronic idle speed control system or a different component, e.g. injection valve or spark plug, is the cause of the problem, the following points must be observed:

1. Disconnect electrical plug from idle speed control valve.

Caution:
Engine speed will increase to 1500 rpm:

2. Reduce air volume by pinching air hose with clamp 000 589 40 37 00 until idle speed is within specified tolerance.

If the complaint still exists, the electronic idle speed control system is not at fault.





The cause can be an internal air leak on the intake manifold gasket between cylinders 3 and 4. In order to confirm an air leak, remove mounting screw (hex socket head screw) between cylinders 3 and 4 and test screw hole for air leak.

3. Check insulating sleeve (2) and injection valve for leaks. If a leak is discovered, replace insulating sleeve (2) and seal ring (3). The following points should be observed.

a. Loosen cylinder head cover to allow proper seating of insulating sleeves.

b. Push 0-ring over insulating sleeve and apply some oil to 0-ring. Insert insulating sleeve.

c. Push seal ring (3) over injection valve and lubricate seal ring slightly. Press injection valve into insulating sleeve (2) to noticeable stop (seal ring to be flush with insulating sleeve).

d. Retighten cylinder head cover.

Engines 116.962/963 and later model 116, 117.

The sealing of injection valves has been improved with a synthetic support ring (3).

For better identification, the insulating sleeve is black. The synthetic support ring (3) can be subsequently installed in previously produced insulating sleeves.





Parts Information: