just-n-time, my question is how hard of a job is it to replace the preformed lines? Do I have to remove the fuel dist.block? Or the Intake Manifold? Any tips to look out for? just-n-time

What do you mean "preformed lines"? Ar you trying to get at the vacuum lines in the intake manifold? If so, you do need to unhook the fuel lines to get the air flow/mixture control assembly off.

Not a big deal to do this.

__________________
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

Yes the large vacuum lines that rap under the intake! they are preformed I thought,they look like they came already molded into that shape? thanks just-n-time.

I think that you are talking about the idle air lines. Yes, they are pre-formed.

__________________
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

OK yes that is,they are they are large and run just parallel of the spray nozzles
I notice after the eng. reaches operating temp.it begins that little rough Idle so I thought it might be those lines leaking.j-n-t

It's possible, but not likeley that the idle air lines are causing the idle problem. It is more likely an injector or injector seal, or possibly a vacuum leak.

__________________
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

I was sure we had a vacuum leak by the slight roll in the idle,that only shows up after it reaches operating temp.so with out spraying flammables all over the place I am trying to research as much as I can into possible places to look, thank you for your reply.j-n-t

Is this a stumble, or a sort of rythmic slight rise and fall in the idle? If the latter, I would replace the oxygen sensor and adjust the on-off ratio if needed.

__________________
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

Yes it is is just a slight rise and fall,not cold but after it comes to temp I was wondering about the electric solenoid in line with the fresh air lines seams as if when it opens the falter begins unless I am wrong about the operation of that valve.It must allow air flow to pass so I thought the leak might be in the preformed fresh air lines. thanks j-n-t.

The best thing to do to fix this is to replace the O2 sensor and adjust the mixture so that youre on/off ratio is right around 45%.

What is happening, I think, is that your sensor is old and not responding to changes in the oxgen/CO level quickly enough. This causes the lambda computer to over-correct, so the engine goes too lean and the idle falls, computer says richen and the idle rises, computer cuts the mixture, idle falls, goes lean and so on.

You can get a generic Bosch 3-wire sensor for about $20.

Lots of posts on adjusting the ratio with an analog dwell meter or a DMM with a duty cycle setting.

__________________
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

Got the picture,I love the electronics of todays autos,if you under stand the links of the system you are in the pink.thank you,I will perform this task over the next week,My Dad just passed with in the last week so I am taking care of all those matters,will keep you posted.thank you again,j-n-t

well I am back, we had a long drawn out affair with the death of my Dad,but I am able to concentrate on the MB now,so I replaced the sensor with a Denso unit,60 bucks.I don't know how to reset the on/off ratio?The problem with the slight rise and fall at idle has not gone away,so I am back to looking for that elusive vacuum leak. j-n-t

JNT-
Read the links in my signature and read this one as well:
http://www.landiss.com/mixture.htm
...for some info on how to adjust your mixture.
You will need a multi-meter (one that has a duty cycle setting makes the job a lot easier) to read the '% on' at the X11 connector.

I still think it is a good idea to unplug your EHA...

to see if the computer has anything to do with the condition.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14

yes I will and I will pick up a meter as soon as I can thanks again,will keep you posted.j-n-t

I am sending some pics to let you know how I made out with the hard lines or preformed lines.I found a crack in this line though I am not sure if this could be my vacuum leak, though the idle air lines might be contributing to the rise and fall of the idle if not sealed? Am I thinking in the write direction?
Now that I have it down this far should I go on and replace all of the idle air lines? Should I go into the seals at the spray nozzles though the nozzles are new,(six months) ago.what of the seal between the manifold half's?how far is far enough?
j-n-t.

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