Hey everyone! Problems once again with the '95 E420. I apologize for the extensive post. Here's a link to the previous posting of the problem and the potential solutions I've tried:

1995 E420 Rough Idle - M119

Problem: The normal slight idle miss has been occurring for the past couple of years but has not been severe enough to really be able to hunt down the culprit. (The list of possible fixes are in the previous post) In a nutshell, the most recent problem occurred following letting the car sit for 3-4 days last week. Upon starting the car, it chugged for a few seconds and died. Fired it again and the engine was idle hunting and then wouldn't do anything but chug on 6-7 cylinders producing a nice sulfur smell from the cats going nuts over the unburned fuel. The miss seemed to jump between cylinders, and when put into Drive the car would simply die.

Most Recent Solution: This shot at the problem was a long one but still a good maintenance job. There was a little oil visible at the top of the #4 cylinder's plug tube so I was guessing that maybe the plug (potentially others as well) had become fouled from oil seepage from the valve cover gasket following the car's sitting. So I pulled the valve covers and replaced all of the gaskets, oil transfer tube seals, as well as new spark plugs. To no avail, upon restart, the problem persisted. NOW comes the screwed up part!!

Because the miss seemed to jump between cylinders we looked once again at the distributor caps. (Mind you, we have replaced them 3 times already) We took out the Right Cap and swapped it with the same cap from our '95 S500 and the car ran just fine. The usual slight miss but no longer any chugging or dying. This points to the cap being shot. (the cap looked fine by the way...no major signs of any carbon tracking) So we installed the same cap on the S500 and the car ran perfectly. WTF???

Am I missing something here?? Why would simply removing and reinstalling a cap have any bearing on how the car runs?? It points to a faulty wire connection maybe but those have been replaced twice already as well. Does anyone have ANY insight into what the hell is going on?? (pardon my French) Voltage related maybe??

PS...no CEL or DM codes, but I am getting an unassumingly related ABS light following maybe 1 out of every 40 or so starts which is a "Solenoid Valve Relay" code....but I'm just assuming it's a dirty wheel sensor.

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1995 E420
1998 SL500 Sport
2009 E350 Sport
1995 S500 Coupe
1992 500 SEL