Rough Idling 560SL

[Strife]

There would be money to be made if a supplier sourced the proper, color coded vacuum line material, connectors, etc (enough to do the entire engine compartment). Assuming that no one has futzed with them, it shouldn't be too difficult to replace them one at a time.

[Roncallo]

To diagnose the problem. I would start by having the car checked out on a scope. With a good scope technician, that will at least give you a good idea if you have an ignition problem.

Its good to try to find a place that will allow you to look at the scope yourself, because usually they will find something stupid like your firing lines or spark lines are too high and say, maybe you should get new plugs cap wires and rotors. While that may or may not be true, you are looking for an obvious problem like which cylinder is different from the others or which is intermittent. Essentially if it is not obvious, your ignition is not causing your rough idel.

It should cost about $50 (maybe $100, I havent done it in 20 years) to have it scoped. A good set of Buer wires are about $180, A cap and rotor is over $100 and the problem may not even be ignition, do you want to guess.

A good scope test will include an ignition diagnostic test and power balance. If nothing shows up in the scope the power balance test should isolate a bad cylinder. If nothing shows up in either then it would be good to look for a vacume leak as that would effect all cylinders. I go with vacume last only because while its cheap to fix they are hard to find.

As far as platinum plugs. MB recomends Bosch W9DC - copper or W9DP - platinum. Its right in the back of your owners manual. I cant find the W9DP's anywhere. But in my 1988 560SL I have Platinum Plus4's, The car runs fine it can exceed the gas milage figures that were originally advertised on the sticker of 14/17. It is the only car I'v ever seen able to exceed the gas milage figures. And it did the 1/4 mile in 15.073 seconds, which is faster than any literature claims this car will do. With the exception of the Bosch Platinum Plus 4 plugs the car is bone stock, no K&N filter of resitor changes ect. The car does have a very slightly (almost unnoticable) rough idel, which may be an effect of the plugs. I will be putting Bosch W9DC's in shortly as my 30,000 miles are up, however these plugs are getting hard to find so I might be screwed.

As far as vacume lines. All of the vacume lines with the correct color striping are available from MB. Now finding a parts guy that will tell you that is another story. But if you have EPC and look them up yourself its no longer a problem

John Roncallo

[stevehilde]

Originally Posted by Strife

There would be money to be made if a supplier sourced the proper, color coded vacuum line material, connectors, etc (enough to do the entire engine compartment).

I noticed that **************.com has the hard vacuum tubing, both mercedes original (expensive) and an aftermarket type (less so). Not sure about the connectors, as I wasn't specifically looking for them when I saw the tubing for sale.

Great idea about a comprehensive package; some enterprising shop should get one together.

Also, it looks like Fastlane, a sponsor of this forum, has the connector pieces, and some types of tubing. Select your year/model, then type in "vacuum hose" in the search engine. Here's what came up for my '85:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1ZW0F8ZE520D1D1CQK&year=1985&make=MB&model=380-SL-002&category=All&part=Vacuum+Hose

[Pete Walls]

RE- vacuum lines, just go to the parts store with samples of each size and buy 10 or 12 ft of each size. It is very cheap.
RE: Platinum plugs...I use Bosch dual contact ones and they work fine
RE: the wires..I threw away all those junky factory ones and replaced them with heavier wires from a speed shop that were made for an American car. cut them and put your own ends on them (furnished) for about $40 bucks.
Definitely plan on replacing all the vacuum lines, even the large ones. I removed one injector and the Vacuum distributor tube broke right off. Was all dried out from old age. there are 2 on the engine, one on each side running alongside the cam cover. I replaced the cap and rotor for about ($125?) i think and thought that was highway robbery (but they are that much for a BMW 6 cylinder so just bite the bullet and spend the money) If you are afraid to try working on a 560 remember that generally these cars are much easier to work on than my wife's Lexus and no more expensive (the local Lexus dealer is getting $125/hr now)

[lexus49]

Originally Posted by Roncallo

To diagnose the problem. I would start by having the car checked out on a scope. With a good scope technician, that will at least give you a good idea if you have an ignition problem.

Its good to try to find a place that will allow you to look at the scope yourself, because usually they will find something stupid like your firing lines or spark lines are too high and say, maybe you should get new plugs cap wires and rotors. While that may or may not be true, you are looking for an obvious problem like which cylinder is different from the others or which is intermittent. Essentially if it is not obvious, your ignition is not causing your rough idel.

It should cost about $50 (maybe $100, I havent done it in 20 years) to have it scoped. A good set of Buer wires are about $180, A cap and rotor is over $100 and the problem may not even be ignition, do you want to guess.

A good scope test will include an ignition diagnostic test and power balance. If nothing shows up in the scope the power balance test should isolate a bad cylinder. If nothing shows up in either then it would be good to look for a vacume leak as that would effect all cylinders. I go with vacume last only because while its cheap to fix they are hard to find.

As far as platinum plugs. MB recomends Bosch W9DC - copper or W9DP - platinum. Its right in the back of your owners manual. I cant find the W9DP's anywhere. But in my 1988 560SL I have Platinum Plus4's, The car runs fine it can exceed the gas milage figures that were originally advertised on the sticker of 14/17. It is the only car I'v ever seen able to exceed the gas milage figures. And it did the 1/4 mile in 15.073 seconds, which is faster than any literature claims this car will do. With the exception of the Bosch Platinum Plus 4 plugs the car is bone stock, no K&N filter of resitor changes ect. The car does have a very slightly (almost unnoticable) rough idel, which may be an effect of the plugs. I will be putting Bosch W9DC's in shortly as my 30,000 miles are up, however these plugs are getting hard to find so I might be screwed.

As far as vacume lines. All of the vacume lines with the correct color striping are available from MB. Now finding a parts guy that will tell you that is another story. But if you have EPC and look them up yourself its no longer a problem

John Roncallo

Can anyone tell me what the 560 Sl stands for? I know it is the model but isn't there a meaning to it? I have a 87 for 21 years now and so many people have ask me, I would like to know. If anyone knows please tell me. Thanks

[gatopardo]

I had a similar problem with my 88 560SL (185,000 miles as of this morning, and running strong). I could not find the source of the problem. I looked everywhere, particularly the vacuum lines, and nothing. Then, one day, while cleaning the air filter, I noticed the vacuum line coming off at the top-back of the engine block (There is an "L" shaped soft rubber connector at that point) was twisted somehow, and when I looked closely I discovered that the connector had a break in the inside angle of the "L," the break was not noticeable to the naked eye, it looked pretty solid, but there it was, a break nevertheless. I changed the connector and the engine was purring as softly as a sleeping cat. I do not know if this is your case, but it will cost you nothing to make sure. Take a look. Good Luck in finding the cause.

[karburn]

My 87 560SL developed a rough idle suddenly...at a stoplight, no less. We have an excellent dealer where I live, but I consulted with the service advisor first and gave him a mandate to check the vacuum lines first. The real problem turned out to be a weak coil that needed replacing and that the previous owner had the wrong spark plugs installed. Runs smooth now. [or should I say FOR now??]

[Alkraut]

Originally Posted by lexus49

Can anyone tell me what the 560 Sl stands for? I know it is the model but isn't there a meaning to it? I have a 87 for 21 years now and so many people have ask me, I would like to know. If anyone knows please tell me. Thanks

"560" stands for 5.6 liter, which is the engine size. "SL" is short for "Sports Leicht", or something like that in German, which I am told is "light sports car". This seems odd since it's the heaviest sports car I know of. Probably light by M-B Panzerwagon standards.

[mrancourt]

I have the same problem. The repair co. says its rusty fuel line, gas tank and related stuff. $ 5,000 should fix it. I have been using Chevron Tecron which is helping. Any better solutions out there?

[450slcguy]

Originally Posted by flixbiz

Can anybody tell me what to tell these guys to do? I'm tired of paying for their speculation!

You need to tell those guy's "adios". $200 buck to swap spark plugs? $600 Buck for cap and rotor? You can buy all those Bosch parts for about $100 bucks or less. Add a good set of wires for about an extra $100. Time to replace all 1.5 -2 hours or less.

Same with the engine vacuum hoses. A few dollars, a couple hours and your done. Nothing complicated here.

[sublettd]

I've gone through a major thrash for about the last 18 months trying to cure a rough idle/loading up condition while idling. After rebuilding the fuel distributor, replacing the warm up regulator, replacing all the vacuum lines, replacing the injectors, replacing all the rubber hoses, checking the timing chain for advancement, replacing the valve lifters, checking all the engine pressures, replacing the idle speed control unit and replacing the idle speed control valve my mechanic suggested about the only possible remaining culprit was a bent valve that might have been slapped by the timing chain--even though the (double) chain and tensioner only had about 50,000 miles on them. So, we pulled the engine and transmission and are in the process of tearing the engine down and rebuilding it.

After the heads were off, it was easy to diagnose the problem. Turns out the problem was worn valve guides. Lots of slop and poor seating at low rpm. New guides have been installed and the heads planed, since they were out of tolerance about .0004. There may be some other problems that we might encounter when the front of the engine is pulled off, but I certainly hope not. Cylinder walls look good.

Interestingly, one cam sprocket was worn almost to a point by the chain and the tips were bent at about a 45 degree angle. It was getting close to a catastrophic failure.

The engine has 147,000 miles on it and, while it ran like a scalded dog, it was a mess. The camshafts are worn--not much but enough that they need to be replaced. Sprockets shot. One of the chain rails on the driver side was broken into three pieces. Four of the 16 rocker arms were pitted.

We're replacing everythign but the pistons and crankshaft--oil pump, oil chain, rings, timing chain, rails, tensioner, water pump, flex discs, subframe mounts, motor mounts, transmission mount, rear pinion seal, and who knows what else. Short of a transmission and rear-end rebuild, the car will have been rebuilt totally. Other stuff has been replaced along the way--brakes, rotors, radiator, steering box, hoses, belts, etc.

Fortunately, my mechanic is letting me do much of the grunt labor to hold the costs down. Even with parts at cost and his labor whittled down, I estimate the finished job will run $5,000-$6,000.

I had to chuckle the other evening while he was working on a lady's SLK 320(?). I was piddling on my SL and she asked if my car is expensive to maintain. I really couldn't answer her question. All I could do was just laugh. If she only knew...

Cheers!