I replaced the ignition system on the 1995 e420 this weekend (caps, rotors and plug wires) to resolve a little bit of a rough idle. Car has 88k on it so I figured it was time to nip it in the butt before the wiring problem got any worse. The problem for the most part was resolved and the motor doesn't even feel like it's on now when sitting at idle. (Smooth as can be)

BUT, here's the catch, in the morning when starting the car, the engine will go through its normal cycle where it holds a higher RPM to warm itself up and then drops down to a normal idle at park and that's when I can feel a little 'roughness' from the engine. It is ever so subtle but is definitely there. After running the car for just a couple of minutes everything is stabilized and the engine runs perfect.

Any ideas? It seems like the car is just dropping the idle a little too low following a 'cold' startup. Hmmmm .

Ps. Wiring harness hasn't been replaced but I'm hoping to get over 100k before having to rip into it.

Any feedback is always appreciated!

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