Date registered: Jun 2012
Vehicle: 1999 SL600 (67k miles), 1998 SL500 (sold, owned from 67k-91k miles)
Location: Los Angeles
Mentioned: 1 Post(s)
Quoted: 29 Post(s)
SOLVED: The new purge valve couldn't really do its job with one of its lines disconnected (see photo). I was poking around in the engine bay per the suggestions in this thread and noticed it. The guy who owns the shop is amazing, but his employees can be hit or miss, and this was an employee job. I brought the car back, they secured the connection with a hose clamp, and the wandering idle was no more. No additional cost to me beyond time and frustration.
P.S. The idle's still not glass-smooth like I'd like it to be, but that's been the case since I bought the car at 55k miles. The tach needle fluctuates ever so slightly, and you can feel the engine kind of fluttering or kicking a little. I'm talking a maximum of 100 rpm either way, but I assume it was rock-steady from the factory with no palpable fluctuation. Would love to bring it back to that spec. I keep thinking ignition coils, but it's never thrown a code for one of those, and in fact the recent CEL was the first one I'd seen in my ownership. Anyway, I'd welcome any thoughts from the V12 veterans on this. Thanks for the helpful feedback on the video.