This problem can be usually traced to a few problems.
Number 1: Due to the fact that you are getting rough idle conditions at random with an intermittent no start I would immediately question the condition of your crankshaft position sensor. This can be either a faulty crank sensor or poor pick up of the sensor. A common issue with this model is moisture penetrating the sensor causing failure. When this occurs in Benz models you will experience intermittent stalls and no starts with no crank. Most of the time the condition seems very random. Eventually the vehicle will be dead in the water when the sensor completely fails. This fault will usually trigger a check engine light, however I have seen them fail numerous times with no codes. See instructions for removal below. This sensor is non adjustable and requires an oscilloscope to test.
Number 2: Camshaft position sensor: Similarly to the Crank sensor, when this sensor fails or comes out of adjustment the vehicle will exhibit rough idle conditions, intermittent stalls, and a no start condition with no crank. See removal and adjustments below.
Number 3: Faulty Electronic Ignition. If you have a blade key (standard car key) this does not apply. However if your E class came equipped with an Electronic Ignition key (EIS) this may be your problem. A faulty EIS will play havoc on even the best techs diagnostic skills. When the EIS goes out many times they will throw no codes and cause intermittent no start and stall conditions. When the EIS begins to fail its basically like turning the vehicle off. It looses signal and then your vehicle will turn off. However with the rough idle condition you describe this may not be the case as usually the vehicle just shuts off.
Number 4: Diagnostic codes? Have you seen any dash lights come since this issue began. Has your check engine light been on? If so I would recommend taking your vehicle in to have these codes scanned. (Autozone will usually do it for free on vehicles '96 and newer) This will give you vital information that will assist in the diagnosis of this problem.
Crankshaft Position Sensor Removal:
1. Sensor is located at the rear of the motor on top of the bell housing.
2. Remove connector and sensor mouniting screw to remove
Top Right box in this drawing is the Crank Sensor
Camshaft position sensor Removal and Adjustment:
1.Remove engine cover
2.Remove camshaft position sensor
To adjust you must remove the engine valve cover
Installation and Adjustment:
1. Replace the sealing ring
2. Rotate crankshaft until camshaft gear segment and camshaft position sensor are positioned opposite of one another.
3. With a feeler gauge measure the distant between the camshaft position sensor and camshaft gear segment.
4. Allowable gap is 0.016-0.024". If it is out of range there are shims available from MB to correct this. They are available in sizes from 0.004-0.40"
Monday, January 19th, 2009 AT 1:56 PM