Look, another M119 Rough Idle Thread!

['flange]

I have recently acquired a really nice '92 400se from along term owner who took care of the car. It idled terribly, sounded like it was misfiring when I bought it. I've spent a lot of time on various boards and forums, looking at other things that folks have done to diagnose this issue. I realize the importance of wiring and the EZL when it comes to timing, and that the EZL will do things like retard timing if it receives spurious inputs. I have a Chinese C5 Multiplexer and can talk to modules. here's the what I've done up to this point.

1. checked wiring harness. all wiring looked good, replaced sometime in the 2000s.
2. checked wiring on ETA, looked good.
3. checked all vacuum lines. everything appeared fine, even the fat rubber lines were still soft and pliable.
3. cleaned the MAF
4. measured resistance of Crank sensor. about 500-600 ohms.
5. inspected wiring for knock sensors. wires are flexible, wires are not cracking or showing deterioration.
6. replaced plugs with F8DC4s. the originals were also F8DC4.
7. replaced Caps and Rotors. Checked condition of insulating rear caps. ok.
8. replaced coils.
9. checked fuel pressure. about 50, holds properly.
10. replaced fuel regulator anyway.
11. removed all 8 injectors, bench tested using carb cleaner/battery method, installed new o-rings, replaced. all appeared fine.
12. measured signal going to coils using a portable digital scope. one seemed lower than the other, which makes me suspect the EZL is putting out a weak signal to one distributor.


On my car, I can only communicate with the EZL when the engine is running. I'm not sure why.. even then, once in a while, communication will be cut and reconnect. maybe a sketchy pin, or a wire from 38 pin to ezl?

After I did these things, the engine is running a lot better and I'm not getting any faults, there is still a "blub blub blub blub" idle that sounds more like a 1950s Chevy v8 than a Mercedes, almost like it's missing. I have not tested the O2 sensor directly, but the LH1 computer tells me voltage is 102-125mv.

I bought a supposedly good used EZL (same part number) off of ebay, and the engine runs significantly worse with it just plugged in, possibly because this particular EZL came with some failure codes on it. I can not seem to erase them as the communication keeps cutting out when I look at the fault memory.

What have I missed? Do I need to start looking at timing chain guides and stuff like that?

thanks

['flange]

Answering my own question. I pulled the valve covers, set to 45 degrees to make sure pins were in alignment. 3 out of 4 were able to pin at about 43 degrees. the right side exhaust cam was out to lunch, and looks like it may have jumped by two teeth. I did not see any broken guides, or any other signs of trouble. any idea why only that cam would jump two teeth?