[W126 Coupe] Slight miss-fire at idle

[malcolm369 at comcast.net]

Hi Pavel,

My 560 did the same thing after sitting winter of 2003, had a slight miss that often would be intermittent. I bought new Platinum Plus 4s for it and while changing the plugs, found corroded plug to wire end connections. Funny too, as F/Motors West had been at it the previous December and replaced a cable end..... Replaced the wireset with a factory set.

Anyway, engine has been smooth as glass since Spring of 2004 with the new Mercedes wires & the Plus 4 plugs. 22,000 miles of smooth powerful and pleasureable motoring. I too use Stabil in my resting cars & lawn tractor and makes a world of difference in my book. I do know others haven't been as fortunate in this regard.

Eddie makes a good point re the little o-rings.

Good Luck 
 -------------- Original message ----------------------
From: Pavel <zhur0002 at umn.edu>
> My 560 sel has been in storage for winter since last october.  I have
> started it for the first time yesterday to charge up the bat and let it
> clean itself out a little. It started good but has a slight missfire when
> in drive or just idling.  The car has just been overhauled completely about
> 3k miles ago and I just had it running perfect before I put it away. It has
> new injectors, euro heads, euro camshafts, euro exhaust manifolds, plug
> wires, dist rotor, distributor cap and a 3.47 rear end.
> Anyways when it first started it idled high about 1100rpm then after 30sec
> it would start to idle inconsistent would go from 1100rpm to 700 rpm and
> back up to 1100rpm.  It did that for about 10 minutes and then it leveled
> out at 700rpm with a slight missfire every few seconds(almost seems like a
> vacuum leak but I could not spot one).  I noticed that I have a fuel leak
> around the o-rings on the altitude box that attaches to the fuel dist,
> would that cause the missfire?  Also I have bosch 4 platinum plugs in it,
> should I switch them?  It ran fine with them before.
> Another strange thing it was doing was, if you rew it up and let of the gas
> quickly it rews down and than stops at 1000rpm for about 10seconds and then
> goes to 700rpm.
> 
> PS.  I aslo stabilized the full tank of fuel in it before i put it away. So
> I'm sure it has good gas. Again it is very slight misfire, but when you sit
> inside the car you can feel the engine running, and that is making me very
> irritated.
> Pavel
> 
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