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1986 420SEL
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I'm a new user here, thought I would say Hi to everyone. I just purchased my firt Benz and now I'm addicted [8D] I used to be a huge sports car guy (still am somewhat), but after driving a friends 420sel I knew I had to have one. This is one of the coolest cars I've driven. They're built like tanks and are pretty comfy to boot.

I bought mine on ebay (kind of sketchy, but for $2700, I think I walked away with a deal). Its an 86 Black 420 with about 157k miles. Most everything works (sans cruise control, sunroof, drivers headrest, all of which I plan to work on) and the interior is in good shape. I put some pics up here http://www.slowlyburning.net/misc/merc/merc.html

Anyways I have a few questions that maybe you guys could help with. Still trying to find a mechanic in town. Local garages will turn the lights off and flip the open sign around to Close as soon as I pull in. All the chain stores (i.e. Sears, Midas, Pepboys, etc..) laugh at me like I've told them the funniest joke in the world when I ask them if they would take a look at my car. The dealership was pretty nice to me, though when you go into the service department they have these curious footmarks on a carpet in front of the counter. Basically it seems that you have to stand on these footmarks and ask for a part/service, then you place your hands on the counter and bend over. I have to say that I am not very accustomed to this type of "service".

1.) What grade of oil do you put in? Where I live (northeast usa) I usually use 10w30 or 20w50 for my other car and truck (celica and tacoma). This is what Toyota reccommends in the manual. However, there doesn't seem to be any reccomendations in the MB manual. Sears said that if they were to "hypothetically" change the oil, they would probably use straight 40. Seems like you would want to use multigrade in my area due to the temps. Any thoughts on this?

2.) Car runs pretty well except for a few gremlins in the idle. From reading other post, It seems to idle about where it is supposed to. However it seems like after it warms up, the idle will go down slightly and oil pressure goes from about 3 to 2 or 2.5, then economy gauge kicks down a little, oil pressure returns to 3 and idle kicks up a little. It does this about once every 2 seconds. Any thoughts on this? I purchased the factory service manual cd's on ebay for $8, and it looks like the only way to adjust idle is with a MB special tool [?] Any thoughts or ideas on this would be greatly appreciated.

3.) Is it just me or does anyone else have problems using the search function on this board? I always try to search before asking questions I'm sure have been answered before (like the oil one) but it just times out everytime I enter something to be searched.

I appreciate the help guys. Looking forward to being a productive member of benzworld.
 

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Depends on the day!
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jwhazel - 3/27/2005 12:24 PM
1.) What grade of oil do you put in? Where I live (northeast usa) I usually use 10w30 or 20w50 for my other car and truck (celica and tacoma). This is what Toyota reccommends in the manual. However, there doesn't seem to be any reccomendations in the MB manual. Sears said that if they were to "hypothetically" change the oil, they would probably use straight 40. Seems like you would want to use multigrade in my area due to the temps. Any thoughts on this?
I'd suggest Shell's Rotella 15-40, should take care of you as well as help clean up the internals of the motor. Also, Never take your car to any of the chains you mentioned...never. They'll just make an expensive mess of things.
Straight 40 weight?? This isn't a pre war car...

[/QUOTE]
2.) Car runs pretty well except for a few gremlins in the idle. From reading other post, It seems to idle about where it is supposed to. However it seems like after it warms up, the idle will go down slightly and oil pressure goes from about 3 to 2 or 2.5, then economy gauge kicks down a little, oil pressure returns to 3 and idle kicks up a little. It does this about once every 2 seconds. Any thoughts on this? I purchased the factory service manual cd's on ebay for $8, and it looks like the only way to adjust idle is with a MB special tool [?] Any thoughts or ideas on this would be greatly appreciated.
[/QUOTE]
Sounds like your idle control valve is on it's way out, or the idle control unit. But it could be a small vacuum leak as well. Check the vacuum off the back of the intake manifold, should be making 16-17lbs STEADY. I've never adjusted an idle on a 126, just fixed the problems that were causing the poor idle.



Jonathan
 

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1991 300 SE
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18,534 Posts
So you’ve got a surge, uneven idle, if the ICV and ICU both check out and there are no vacuum leaks, look at the following next

Bad Distributor Cap and Rotor

Faulty CIS Coolant Temperature Sensor

Failed OVP Relay

Dirty Throttle Body

Failed O2 Sensor

Bad throttle position switch

With the year and miles on your car the injectors may be worn or leaking.
There is also an electronic adjustment valve located on the fuel distributor (known as the EHA) that can leak or fail causing a rough idle.

Jonathan’s right about there being no idle adjustment for the CIS fuel system per se, some of the system’s components may need to be adjusted but once the weak link is replace or repaired the idle should be corrected.

Oh, and I almost forgot: welcome to the forum and the 126 family.
[:)]
 

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1985 300SD
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I used to live in NE PA. Before I didn't have time to work on my car. I used to take it to a guy near Hazleton, PA. I could get his number if you want. His hobby is MB cars. At any given time he has 5-6 behind his house. I only took my car there once but my brother in law knows him fairly well. You only list Central PA so it may be a bit far for you.

Your best bet is to but some tools and ask alot of questions here.
 
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