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  #1  
Old 08-01-2003, 04:35 PM
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Join Date: May 2002
Location: Washington, D.C.
Posts: 395
ARRGH!! Please tell me I didn't do it....

So yestrday I decided to do the timing chain on my 560 SEL. Also the rails.

I removed all rockers, placed them each into an individually labeled ziplock bag.

Of course the plugs where removed.

So I rolled in the new chain (bought here at FastLane). I vice-gripped the incoming and outgoing chain on the passenger side cam sprocket. The connecting link came out perfect (i.e. correct chain length) - I checked all three timing marks (two cams and crankshaft), all seemed accurate. Then I replaced the tensioner, checked all thre marks again, and the most I could detect was perhaps a 1-2 degree difference on the crank marker (i.e. not exactly zero, but a hairline off). Checked the cams were both right on the dot. There never was any jumping of the chain (how could it - no compressension and no valve spring tension).

Yet when I started the car, which it did right away, it idled roughly. Drives great, by the way, but the idle is rough.

Should I look at all the vacuum lines again, or did I screw up?
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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)
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  #2  
Old 08-01-2003, 08:39 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
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If it runs well, you didn't bend anything, and if the timing marks are in line, the chain is perfect.

Your rough idle is another problem. Start with looking for a vac leak, certainly, but don't ignore the secondary ignition system -- bad plugs, wires, cap, or rotor will give a rough idle.

So can a bad engine mount, by the way, check those too. If you have the spherical gell filled ones, if the rim is less than about 3/4" from the frame, you cannot see the tapered portion on the bottom, or you find sticky goo on it, it's shot.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #3  
Old 08-01-2003, 09:03 PM
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Join Date: Apr 2000
Location: Falls Church, VA
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I agree with Peter. You may have inadvertantly disconnected a vacuum line, or caused a brittle connector to break. I would also check the ignition timing, which may have changed with a new chain.

There is also a long post on a similar problem 3-4 months ago.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #4  
Old 08-02-2003, 12:02 AM
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Location: Washington, D.C.
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Thanks for the reassurance!

The pickup is great - better than before. It's only in the idle.

I suspect the secondary ignition or the vac.

What a job this was! The right side (passenger side) cooperated fully - the left side (driver's side) I could not pull the pivot pins for the guides, nor could I pull the distributor retainer bold. I will let a shop here handle those (broke a bolt in attemtepting to pull a pivot pin). I suspect the the left side (driver's side) runs hotter on the v8 - there was a significant difference in the valve cover gasket hardenss between the two sides.
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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

Last edited by hbofinger; 08-02-2003 at 01:42 AM.
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  #5  
Old 08-02-2003, 11:18 AM
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Location: Gainesville FL
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One thing I might note:

When you removed the rocker arms all the good hydraulic lifters fully extended. When you replaced them they usually don't reced automatically. This is where the lifter tool comes in handy by showing the extention of the ball socket.

I have reassembled the rockers and the car wouldn't even start due to this occurance. WE now automatically verify each ball position after disassembly. We have even built a lever tool to drive the installed lifters down (the spring pushes them back with oil reinforcing the position when disassembled)
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Continental Imports
Gainesville FL
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  #6  
Old 08-02-2003, 01:12 PM
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steve - interesting note. But I still wonder if that has anything to do with the symptoms I am experiencing.

The idle has always been a touch rough. It seems that having replaced the chain increased, rather than decreased, the symptoms. And again, the pickup and the drive is perfect - no complaints there.

I know the timing cannot be adjusted - it's all computerized, so messing with the distributor won't help.

What I do wonder about is the following - what if the old chain was streched and had jumped a tooth on the crank (not the cams)? I would have kept the error because the new chain went in tooth by tooth, and the tighter chain would have knocked the timing off even more. Would one tooth on the crank have caused a catastrophic collision (if yes, I KNOW that's not the problem, because the engine performes well), or would I be having the exact symptoms I am having? I thought the crank was off by 1 degree or so, but I attributed that to simple machining slack.

I also wonder if a timing light could give me a clue as to what is going on...

The car has 104,000 miles. Secondary ignition all has about 5k miles. I hear no vacuum leaks, though I will investigate further...
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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)
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  #7  
Old 08-02-2003, 01:18 PM
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Location: Washington, D.C.
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Actually, come to think of it, that scenario is highly unlikely. The crank pulls the chain, so there is always tension there, even on a loose chain. If it had jumped, the cam allignment marks would have shown it...
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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)
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  #8  
Old 08-02-2003, 02:46 PM
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Yes, the chain would jump ahead of the cam if it slipped and the cam would be retarded which would have been improved with a new chain even if in the wrong link.

idle roughness is either a symtematic lean condition or a specific one on a 560 in closed loop. Try running the engine with the air cleaner off and slightly depress the air flap. If it instantaneously improves the idle the above conditions are proven.

To tell whether it a systematic of single cylinder problem open the lines from the fuel dist to the injectors one at a time sopping up the small amount of freed gas and watching how the engine runs. A distinct misfire will occur on good running cylinders. Poor running cylinders won't make much difference.

If they are all the same and the engine responds to the air plate deflection then you must see if the engine is running in closed loop before proceeding.
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Continental Imports
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33 years MB technician
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  #9  
Old 08-02-2003, 03:29 PM
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Steve,

Thanks for the excellent advice. Yup, the chain would have jumped on the passenger side cam right after the tensioner. So I'm not worried, and I will follow your diagnostic tree.

One last question - what do you mean by closed loop?
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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)
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  #10  
Old 08-04-2003, 10:24 AM
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Join Date: May 2002
Location: Washington, D.C.
Posts: 395
Lightbulb UPDATE

OK, it all makes sense now. I kinked the fitted fuel supply line going into the fuel distributor on removal (did not counterhold the female end until I realized what was happening). So the rough idle is cause by lack of fuel pressure in the fuel distributor caused by a narrowing.

Off to the junkyard... (with tools...)
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1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)
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