380sl vacuum lines

[JustJim]

Can anyone tell me what vacuum lines run under the intake on the 1982 380SL? Also, does the intake manifold have to be removed in order to access all vacuum lines? Thank you.

[meltedpanda]

I don't believe any run under the intake, there is one from the manifold and one to the throttle body, but none "under" that I know. THis schematic is from a 380sl -1985, don't know it it will help or not. What specifically are you trying to do ?

[JustJim]

Trying tomake my engine run right. It won't idle down. The local shop told me they didn't work on the "old ones" but I probaply needed to change the fuel distributor. When that didn't change anything, theytold me new fuel injectors. Other rhan costing m a lot of money for th new items, nothing has changed. The latest advice was to pull the intake and look for leaks. I bought the gaskess but other than two lones to the throttle body in the frontand one vacuum line at the back of the intake manifold I don't see any other lines. Wanted to make sure I' need to remove the manifold to find a missing line before I spend more money and labor and end up withthe same condition again.

Do you have the table that identifies the numbered components onthe diagram?

Thank you.

[JustJim]

Almost forgot, also replaced the fuel pump and filter.

[meltedpanda]

have you checked the auxiliary air valve to make sure it is closing off?
That is a common issue for high idle. the manifold does have gaskets at the intake, if they are bad it will also result in high idle.

[JustJim]

Where is the auxiliary air valve located, what does it look like, and how do you test it? Another problem, I don't know if it is related, the electric cooling fan seems to always be on any time the key is on, and the engine doesn't seem to be getting too hot, at least according to the gauge. Didn't think much of it before...

[timm9]

I have recently sold my 82 380SL but do believe that there is one vacuum line that runs 'under' the intake. I discovered it after removing the intake to replace the 'air chamber' that had 7 larges cracks. If memory serves it runs from the general vicinity of the cold start valve (driver side) then under the intake towards the rear of the passenger side. I thought I had photos but apparently not at my office. I will check at home.

[timm9]

I spent several months and quite a bit of money chasing the high idle on my 82 380SL. After all that time and testing and part replacements I finally got smart and hauled the SL to a shop to be smoke tested. Within 3 minutes of the smoke test it was rather obvious why I had the high idle. The air chamber had 7 large cracks allowing too much air into the system which was telling the analog brain to add more fuel.

The smoke test was $100.00 which if I had done to begin with would have saved me 5 times that in parts.

[JustJim]

I haven't found a smoke machine around here yet. I'll keep looking. One of the shops must have one. By the way, by "air chamber" are you referring to that rubber boot under the air flow meter? If so I replaced that too...

[timm9]

Jim,

Do a search for my 'user name' timm9 and you will find posts with photos. You will see the air chamber which is about $85.00 had major cracks. It does require the removal of intake, fuel lines, etc. to be able to get to the chamber. The first time I did it (another story...) it took me several hours as I was painstakingly documenting each step for my own benefit. If this ends up being your issue as well let me know so you don't have a 'second time' story to tell...

[JustJim]

Did the search and found the air chamber picture. That is the same as the air flow meter boot I replaced earlier, just a different name. I saw that you had problems getting it to seal to the plate. Maybe that is also my problem...
I'll have to check on that.

[timm9]

Jim,

If you have already replaced the air chamber and have no vacuum leaks then it has to be something else. Have you or anyone else 'adjusted' the duty cycle? Until the engine reaches temp (80C I think) the analog brain and O2 sensor do not control the idle. If you suspect the warm up regulator (WUR) you can easily pull it and clean with carb cleaner and see if there is any change. You will not see any change if the engine is not yet up to temp. If 'no one' has messed with the duty cycle I would suggest leaving it alone unless you have experience.

[JustJim]

Not sure if all the vacuum leaks are solved, which was why I initially asked about vacuum lines beneath the intake manifold. I already bought the intake gaskets and pulled the fuel distributor and metering valve, but I only see the 2 connections on the throttle body and no other vacuum lines below the manifold. I don't want to be missing a possible leak because I didn't see the line, but I also don't want to pull the intake if there is no reason to. I can remove the air chamber you mentioned, but not sure I would be able to tell if it was leaking or not. Also, I don't know what the "duty cycle" you mentioned is or how to check it. When cold the car starts easily, the aux fan runs constantly, and idle is 1500-1800 rpm. When warmed up nothing changes, except is hard to start. Also, i unplugged and rrmoved the computer from under the passenger floorboard and absolutely nothing changed. Again, I don't know if that means anything. What should I be looking for?

Thanks for your help and patience. This is my first 380sl.

[timm9]

Jim,

Your comment about the aux fan running non-stop triggered something in my memory; I did replace the temp sensor next to the WUR and if memory serves me it did help at the end. When I was dealing with high idle I also looked to the analog brain under the passenger floor but after careful inspection I could not find any broken or questionable joints after opening the unit and inspecting the circuit board. You might want to open the case on the analog brain and inspect the circuit board.

The reference to 'duty cycle' is MB's term for the fuel mixture and what is called Lambda. It would not hurt you to do a little research and there are many posts on the subject. With Lambda there is no 'idle' screw to adjust. The fuel mixture is completed with a quality meter with a frequency setting that allows you to properly adjust the mixture. Some techs that are not knowledgeable will try adjusting the fuel mixture assuming it will control the idle which it will not. The 'individual' that attempted to smog my 380 had it so screwed up I was getting 9 to 10 miles to the gallon and staining my garage floor at idle it was so rich.

If you have confirmed that all of the vacuum leaks are fixed then (going from memory) I believe the next thing I tackled is the O2 sensor. It was under $30.00 and does play a direct role in proper fuel mixture once engine is up to temp. The other less expensive item I did change out was the Oil Temp Sensor which is located near the oil filter on the passenger side closer to the front of engine. Hopefully this makes sense. I'm working 'backwards from memory as I did not find the cracks in the air chamber until after replacing these parts.

Jim, I don't profess to have all the answers but I'm willing to help. When I was dealing with this issue a gentleman on this site went above and beyond for me so I see this as an opportunity to pay it forward...

Tim

[Wrightbenz]

Two lines go under the intake right by the throttle body, not the airflow meter the throttle body. They are very hard to see and connect with 2 rubber elbows to the ports under there.