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  #1  
Old 08-16-2007, 04:00 PM
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Join Date: Aug 2007
Location: Charlotte, NC
Posts: 76
560SL tuneup

My car is an ’87 560SL and I am having some problems with the idle:

Initial situation:
-very hard to cold start
- rough idle
-black/blue gas smelling smoke coming from exhaust for the first few minutes after start

Remedy so far:
-new cold start valve
-new plugs
-new wires
-new air filter
-new distributor (not yet installed)
-new rotor (not yet installed, broken upon arrival from dealer)

Current situation:
-starts cold like new
-runs a little smoother
-still black/blue gas smelling smoke for the first few minutes.
-seems difficult to start when warm

So my question to the brain trust is how you all suggest that proceed. I am thinking that I might have a vacuum leak somewhere affecting the gas air mixture and resulting in the smelly exhaust. That might also explain the rough idle. I am I little unsure what the hard warm start could be; maybe the EGR valve or a vapor lock in the fuel system. I am also trying to determine if a new O2 sensor could help.
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  #2  
Old 08-16-2007, 08:34 PM
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Location: Falls Church, VA
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Suggest checking out the coolant temp sensor at the front of the intake manifold. If it's sending bad data to the computer, it may be responding with too much enrichment. There are very specific vaues for resistance at various temperatures on the CD.

A new O2 sensor and a mixture adjustment if needed can't hurt.
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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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  #3  
Old 08-16-2007, 10:14 PM
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I have a similar issue, i have a 84 380sl that is also hard to start from cold. when i run it on the highway and come to a stop it idel's very high. any suggestions
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  #4  
Old 08-17-2007, 09:58 AM
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The '84 380SL doesn't have the temp sensor like the 560. The cold start problem could be the warm-up regulator, or a very lean mixture setting, leaky fuel accumulator, leaky injectors, or all of the above. If the temps don't go below 55 at night where you are, it's probably not the cold start valve.

Your high idle could be the idle relay and/or idle valve, or a vacuum leak, or dried-out injector seals, or some or all of the above.

Lots of posts on all these topics will come up in a Search.
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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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  #5  
Old 08-17-2007, 02:28 PM
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Quote:
Originally Posted by ctaylor738 View Post
Suggest checking out the coolant temp sensor at the front of the intake manifold. If it's sending bad data to the computer, it may be responding with too much enrichment. There are very specific vaues for resistance at various temperatures on the CD.

A new O2 sensor and a mixture adjustment if needed can't hurt.
On the CD are you referring to 073-121 (p11) for the coolant temperature sensor?
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  #6  
Old 08-17-2007, 03:50 PM
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My CD hasn't worked for a while, I think because it needs ancient versions of Flash and Acrobat Reader.

The section I was referring to has a little table of resistance values that the sensor puts out at different coolant temps. The sensor has four contacts. You measure diagonally across the contacts, IIRC.

The replacement that I bought was off 10% from the values but seems to work fine.
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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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  #7  
Old 08-17-2007, 04:00 PM
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Sorry to hear that. Is this the PDF? http://www.overgaardweb.com/dl-files/073-121.pdf
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  #8  
Old 08-18-2007, 05:15 PM
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That's it.
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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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  #9  
Old 08-18-2007, 10:59 PM
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So there is a table with resistance to temp but how would you go about finding the temp in order to verify that the sensor has the correct resistance? Would a termometer in the coolant do the trick?
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  #10  
Old 08-19-2007, 09:27 AM
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You can do that, but if the car has sat overnight, the air temperature works fine. Don't wworry about getting too exact, you would need a resistance value that's 'way off to cause the symptoms you describe.

So 70 F is about 21 C, and you should see about 2.5K ohms across the pins. If you see 5K, then that's a problem, but I wouldn't worry about 3K.

Good luck.
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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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  #11  
Old 08-19-2007, 10:58 PM
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Location: Charlotte, NC
Posts: 76
Did you just measure on value? -or did you warm the sensor? It could be possible that the sensor doesn't fit the curve (temp vs. ohm). I suppose that you could warm the tip of the sensor up in hot/warm water?
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  #12  
Old 08-20-2007, 06:10 AM
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I just measured at the sensor, and compared the reading to roughly what I thought the coolant temp was. I think I then started the car and measured it again when the gauge hit 80.
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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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  #13  
Old 08-21-2007, 09:15 AM
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Location: Charlotte, NC
Posts: 76
I was looking at the diagram for the injection system and I must admit I am a little confused. From out discussion so far I am understand that you think that the coolant (engine temperature) sensor might be failing. One way to check if that is the case is to take a couple of measurements across the sensor and see if they are within spec per the table in the above PDF.

Now, looking at the diagram (http://www.overgaardweb.com//dl-files/073-013.pdf) I see that the sensor is marked B11/2 but I do not understand how that is controlling the EGR valve. The only two valves I see that could influence that are the two vacuum valves marked 79. They are also monitoring the coolant but since they are vacuum valves you cannot measure any resistance across the pins. Both vacuum valves are connected to the vacuum amplifier (90) which connects to the EGR and controls the open/close through the vacuum.

If the EGR is involved wouldn’t it be a better guess that the vacuum valves are faulty rather than the B11/2 sensor?
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  #14  
Old 08-21-2007, 10:01 AM
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It doesn't control the EGR valve. It tells the ECU, through the resistance value, what the engine temperature is. If it is faulty, it could tell the ECU that it's 0 degrees when it's really 70, and the ECU will richen the mix to compensate. This is to address your problem of black smoke on warm-up.

The other vacuum switches are there to ensure that the EGR doesn't open until the engine is warm enough.
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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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  #15  
Old 08-21-2007, 06:15 PM
Bob's your uncle
 
Join Date: Aug 2007
Location: Charlotte, NC
Posts: 76
I made 3 measurements:

Ambient: 3.1 KOhm
60C: 800 Ohm
80C: 700 Ohm


Ambient air temp in my garage is about 85-90F (30C) so I am guessing that the engine is about 20C

Assumeing that the temperature is correct the values per the table should be 2.5 KOhm, 600 Ohm and 325 Ohm. It seems like the cold resistance is fairly much on par while the higher ones are 50% off. However, since the smoke is during cold start and the low temp resistance pretty close to what is expected and am not sure that the temp sensor is the problem.
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