1992 400E (124.034)
Okay, fighting an ongoing battle: Rough cold idle/drive/hicupping is an intermittent problem - things are fine on start-up, then when the car drops down to 500rpm things get rough. Goes away after engine warms up briefly, is turned off, left for a bit, but not all day/night and re-started.

Sparkplug wires showed evidence of arcing - which would cause the problem, so I replaced, with no resolution - so a couple of questions:

1. My Premium Bosch wireset (marked for V8 Mercedes) has 11 pieces - Uuuuum, does my car use an 11th wire - if so where? It' the same as the shorter of the two coil wires - am I missing something critical?

2. What other issue would consistently be "resolved" by such a brief, if spasmatic, drive: only several miles, and car usually runs fine when restarted.

3. Finally, despite never having had any warning light (ie..check engine or otherwise), is it likely that a code reader could diagnose this, even if the car is apparently running fine at that moment of the reading?

Vielen Dank, Scotzbenz