[W126 Coupe] Rough idle

[Marcus Johnson]

Hello all,

Have had the car to the mechanic for a tuneup but now it's idling 
(slightly) rough.

It was running beautifully when I took it in, smooth as could be. Now, 
after three tries, it is still a bit rough.

He has replaced the plugs, leads and rotor. Also checked the fuel 
filter, put it on the scope, etc.

I'm wondering whether his choice of aftermarket leads – not MB or 
Bosch, some name I've never heard  of –
could be causing the roughness.

I seem to recall discussion about how these cars run better with the 
OEM leads.

A quick search of the archives hasn't pulled up any data yet.

Thoughts?

marcus johnson
380 SEC
Melbourne, Australia