Idle havoc and brake issues! Help! 3.5 V8(M116.980) - Mercedes-Benz Forum

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post #1 of 1 (permalink) Old 02-27-2008, 01:07 AM Thread Starter
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Date registered: Jul 2005
Vehicle: '68 280SE (w108), '72 280SE 3.5(w108), '88 560SEL(w126), '97 E50 (W210
Location: Cebu, Philippines
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Idle havoc and brake issues! Help! 3.5 V8(M116.980)

Hi all! Haven't driven my 3.5 for the past 3 weeks. When I started her yesterday there was a loud pop right in the air cleaner, and smoke came out of the air cleaner mouth. Guess she backfired right through the throttle body. Started her again after I removed the air cleaner and checked for loose connections, and although there wasn't any loud pops, it was replaced by a series of intermittent little pops. And the idle was seesawing nonstop. I tried removing the spark plug cables one by one to see which cylinder was doing this, and I could only verify that 6 of them were not the source (I think, since I could still hear the popping). I couldn't reach/pull out cables for the number 4 and 8 cylinders, it was dark and hard to access. I'll try again. Before the backfire issue came the idle would seesaw a bit, but she would settle down after a few minutes (I assume when the engine has warmed up a bit).

Started the car again today and the same thing. Seesawing idle, mini pops in the engine. I'm hoping to get some time off with the weekend coming up so I can resolve this issue. What seems to be the problem? Rich mixture? Sitcking valves? Has anyone experienced this? Your advice is greatly needed and appreciated.

And one more thing, when I put the car into gear it takes a lot of brake pedal effort (floored and stomped on hard) to keep her from going, especially in R. But if I shift her into N while she's creeping the brakes bite right away. Would this be related to my problem above? Or would this be a separate issue? Please enlighten me with your inputs. It's frustrating enough not having the time to drive the car, it even worse when the car refuses to cooperate when I have the time to use it.

Thanks everyone!

'68 280SE (w108)
'72 280SE (w108) 3.5
'88 560SEL(w126)
'97 E50 (W210)
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