Rough idle

I have this question and I hope that someone can help me out here due to the lack of time I have to look at the car much myself and the language barrier.

My car 1989 Mercedes 560SEL 227,000+miles have developed a rough idle, but steady. It never stalled, it doesn't even sound as if it will stall and holds normal idle speed. There has not been or is no smoke from the engine even with the oil filler cap removed. Also, there have been no significant power loss. It stills shoots off the line like normal and expected and is smooth all all speed until it is standind still idle. The only weird noise I hear is the sound of a slight exhaust leak around the exhaust manifold area, which I will track down as soon as I have time but I don't know if this have or would have anything to do with the idle problem but they have both developed at the same time. I haven't tested the idle components yet, but I think something there is also suspect but could the exhuast and rough idle be a coincidence or could they be related?
Now I'm sure I can track down the problem once I have time to actually track it down, but since I really haven't post a problem in a while and we are all here to assist each other I just thought I throw in a bone. And advise and opinions will help me save time which is very very appreciated.

And I need a center armrest leather replacement. It's cracked, torn, and time to replace it. The cushion is still perfect condition and would like to keep it that way so I need the leather for it to make the interior look way nice.

Exhaust leak could be linked to rough idle.
Correct this before spending time on the long list of other possibilites.
Stuart

How about plugs? Wires? Adjust the idle also it might make a difference.

There is a vaccuum connector that goes to a small vaccuum capsule that comes off the intake, below the air cleaner, more toward the back on the passenger side. On my 560 engine that sometimes slips off - needs a new rubber hose connector between engine vaccuum port and capsule, I guess. Anyway, that always leads to just the rough idle you describe, with no stall. Just make sure all vaccuum hoses and connectors are intact.

Plugs and wires have been replaced around the same time the water pump was replaced, April 2006. Just as a measure and prep for shipping to the German autobahn and since I never knew the last time they was replaced. The mechanic saw nothing unusual about the old plugs/wires. Thanks for the info. I will check this stuff tomorrow and it help me pin point things and probably saved me alot of time.

I'm sure I have an exhaust leak so I will definately check that out and pinpoint it so it can be fixed ASAP, because the noise is a little annoying too. Then check then intake and vacuum hoses and connectors and go from there. I'm not worry about too much about the extent of repairs. Hey this is Germany and parts from the dealership is usually way cheaper than even buying them online wholesale price, then I found a couple of good mechanics that see BMWs, Mercedes, Audis all the time and been working on them for years but don't charge too much of an arm and a leg for the work like in the states.

The goal is that by the time me and this Mercedes return to the states, it would be in total perfect or as close to perfect condition as possible with a couple of upgrades.
Even being in Germany where I thought I would blend in, this car still stands out. I get compliments from Americans and Germans alike. One German told me that it's rare to see a W126 V8, let alone a 5.6. Then even rarer is the long wheel base.

They have to pay a very high tax on motors that big.  And as you have found by now, the petrol is sold by the liter at a higher price than our gallons.   I'm sure you found a local to fix it by now, but is the idle rpm and what hapens to it when you pull the vacuum?

Much higher price!
In the UK petrol (gasoline) hit almost 8USD / US Gallon about two months ago!

Note: UK Gallons are 25% bigger than yours?

Stuart

No wonder I get so many compliments. Before I got here I thought these W126 5.6s were a common place but they are a very rare sight. In fact, I've only seen a couple of 500s and mine is the only 5.6 I've seen so far. Seen a couple for sale in the paper in Frankfurt but they are going for $6500+ and some don't have all the options you find on the American version. And the gas for this thing over here is about $1.25 euro a liter. or about $6-$7 a gallon
 

quote:

ORIGINAL: garymand

They have to pay a very high tax on motors that big.  And as you have found by now, the petrol is sold by the liter at a higher price than our gallons.   I'm sure you found a local to fix it by now, but is the idle rpm and what hapens to it when you pull the vacuum?

About 100 Euro a tank for my car.