I bought a 94 E320 3 weeks ago, it was fine . just yesterday i was warming it up I found it shakes and then go smooth and may be after 20 seconds shakes again and keep doing that. it do that when it is on park on D in the stop lights.I would like to find out from anybody in this forum for suggestions, why is that ? thanks for the help

 

some of them found the wiring harnress on the engine bad.

you can move it while the engine is running to check.

 

thanks for the reply, where I can find the wiring horness?

 

I suspect a bad Overvoltage Relay. These were a troublesome part on 123.032 and have been upgraded.
The relay is a tall aluminum can w/fuse on top.. behind the firewall panel [ blk plastic] on the passenger side. If the original relay is still there , change it to the newer part #
Old part # 000 540 52 45 [ Siemens manufacture]
New part 000 540 67 45.
I also recommend changing the 3 plug connectors/resistors under each coil. Another common problem area on HFM/SFI waste spark ignition systems.

A Dalton
Benz Tech/Collector

As SL noted , ...The wire harness issues with these was insulation degradation due to the use of bio-degradeable materials. You can usually find flaking insulation at the sensor connectors at the thermostat housing. Most of these have been upgraded by now.
Is your car showing a Check Engine light ???????

 

there is no check engine light, but the thing is when I turn the key all the lights comes on (air bag, oil,..) except the check engine stays off

 

Ok
If no CE light , your car is not Cal spec. [ Emmissions module N59], but Fed spec [ I am assuming you are in USA??

Under the hood , in front of battery..blk box with lid .. open lid and see a 16 pin/socket connector.
You can retrieve fault codes from this box with a simple $5 DIY tool.
Check that box and tell me if it has a sw/led in positions 2 and 4.

 

there is a check engine light but it does not goes on with the rest of the lights when I start the car

 

Is there a sw/led in the box I mentioned ???.. that will tell me if you have a CE light system...

 

I had this problem before and it was the computer. I replaced the overvoltage regulator and that did not fix it.
For the wiring connector, I cleaned it with PCB board cleaner to eliminate poor contacting.
You should also check fuel system. A bad injector can caused misfire.

 

If you are talking about your E420. it does not have an OVP.. I think you are confusing the voltage regulator and OVP.. different part/function..
The most common misfire fault codes on 104 engines are caused by the 3 plug connectors under each coil. This is a waste spark system and each coil fires 2 cylinder at the same time, in series. So, bad coil connectors cause misfires in both cylnders
Due to there high failure rate and cheap cost [ $9 ea], we change them whenever doing a plug change.

PS . Use only Bosch Super copper core plugs in 104s , never plats ...
Bosch F8DC4.