Mercedes-Benz Forum banner
1 - 20 of 99 Posts

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #1 · (Edited)
I first off want to thank all of you wonderful MB owners (fanatics) for providing great information that has been invaluable in my attempt to revive my recently purchased gray market 1981 280sl 4 speed. the car is up and running now thanks to the threads that included vacuum diagrams.
Now I am hunting for the ECU(?). The computer that the O2 sensor plugs into. I can see the O2 sensor installed in the exhaust with a lead with a spade terminal on the end hanging down connected to nothing. I have looked in as many places that are mentioned on this site (firewall, behind glovebox, passenger kick panel by the fuse panel, etc.)for the computer to reattach the lead and can't find it. Am I looking for the wrong thing? Thanks for the assist, docborg.
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,777 Posts
Welcome to the 107 forum. Please check your sanity at the door.

Sounds like a nice car. Manual trans is very desirable. Post pictures when you can. In answer to the ???????? in your profile, yes. All 280SLs are gray market in the US. Some were Federalized more than others on import. I have an '81 that had nothing done to it. It does not have an O2 sensor. I don't think it has an ECU.
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #3 ·
Thanks for the info. The car seems to have entered the US through Houston. It may not have a computer on it. The inporter did some smog control. There is a hollow metal tube that runs from a valve in the exhaust, over the top of the engine and enters the intake. I reattached all of the missing vacuum lines to the WUR etc. The idle is not extremely high now. I still get some RPM variation when warm. Just seems odd that they installed an O2 sensor and no place to connect it. (Maybe my old eyes haven't found it yet)!
 

·
Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
Joined
·
6,050 Posts
That metal tube is the EGR not an O2 sensor. the valve itslf is on the exhaust manifild and is activated by vacuum.
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #5 ·
That metal tube is the EGR not an O2 sensor. the valve itslf is on the exhaust manifild and is activated by vacuum.
Absolutely, just trying to fill in some information about the smog that is on this particular car. The O2 sensor is screwed into the exhaust low in the enginebay and has a single lead wire running from it about 6 inches long. connected to nothing.
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #6 ·
Pictures of docborg 280sl

Absolutely, just trying to fill in some information about the smog that is on this particular car. The O2 sensor is screwed into the exhaust low in the enginebay and has a single lead wire running from it about 6 inches long. connected to nothing.
Pictures of the 280sl
 

Attachments

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
12,269 Posts
Absolutely, just trying to fill in some information about the smog that is on this particular car. The O2 sensor is screwed into the exhaust low in the enginebay and has a single lead wire running from it about 6 inches long. connected to nothing.
Maybe someone installed an aftermarket air/fuel ratio gauge for tuning purposes? Could have been removed or perhaps a portable unit.

I don't think cars had O2 sensors at that time did they?
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #8 ·
Good question. I have a Haynes 123 manual (1977-1981) that shows this type of engine with catalyst, ECU, O2 sensor and air pump. It is described as late emission control system. My car does not have an air pump.
 

·
Outstanding Contributor , Bob's Your Uncle!
83 280 SL- 5 speed-The PIG
Joined
·
32,165 Posts
My 83 280 SL came to me with a bunch of phantom wires going no where but seemingly used for some fuel management system somewhere along the line in it's life.

I have the EGR valve but the hardpipe to the intake is under the front of the engine.
I also have an aftermarket charcoal cannister.
But that's it.
No ECU and no O2 anything.

I wish my car could talk.
 

·
Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
Joined
·
6,050 Posts
I wish my car could talk.
__________________
^^^ You do enough for the two of you.
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #12 ·
OK. Having looked at Pex's, petesmga, and nobby's posts it gets more interesting. I have a frequency valve that is not connected to the O2 sensor controller. I can't seem to find the O2 sensor controller (seems it is also called a Lambda controller. Maybe someone removed the controller because it was faulty? On cold start up the car idles at about 900, rises to 1300-1500 for 4-5 minutes and then drops to 700-800. After well warmed up the idle hunts and pecks...900 down to 550 and stumbles then repeats. Bit of a hard start when hot, smells overly rich. Was thinking that the connection of the O2 and controller to the freq valve would help.
 

·
Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
Joined
·
6,050 Posts
It sounds like you have a faulty WUR and a vacuum leak. The frequency valve thing is probably a dead issue. Try disconnecting on cold start and see if it makes a differece. I will do the same on the 84 tommorrow.
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #14 ·
Could be. The WUR had no vacuum lines going to it when i got the car. replaced both. Could easily be inop. Lots of fun to get to. Had to remove oil filter.
 

·
Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
Joined
·
6,050 Posts
Found the ECU and lambda controller under the passenger foot board.
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #16 ·
Looked there, but can't seem to locate them. Are they in a double secret hiding place, or am I just missing them. I had the under dash panels off of the passenger side today and had the cover off of the fuse panel. Nothing I can see that looks like the pictures of those controllers. Did you have to remove anything special to see them?
 

·
Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
Joined
·
6,050 Posts
Pull out the carpet and backing, there is a plastic panel where you would rest your feet on the firewall, a couple of screws and your there. Passenger side
 

·
Registered
1981 280sl 4 speed (gray market car?)
Joined
·
46 Posts
Discussion Starter · #18 ·
Thanks, I will look again. I had carpet out today and did not see any plastic panels, seems to be all metal. Could have missed it. Will look again tomorrow. Too disgusted to look tonight. Had to replace the battery in the 280 today. This Benz reacts very strangely when the battery is in bad shape. New battery at Wally World and it started right up, with a bit of a high idle of course.
 

·
Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
Joined
·
6,050 Posts
Hey doc, do you have a frequency valve as shown in Pex's picture? If you don't you don't have an O2 sensor or ECU. It may have come with the replacement engine pipe. My 79 280sl has no ECU or lambda control. As you stated there's just metal behind the carpet on that car.

Auto part Engine Fuel line Vehicle Electrical wiring :thumbsup:
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,777 Posts
Doc. I will try to snap a couple of pics of my '81 tomorrow. Can you see the O2 sensor from the top? If so which side?
 
1 - 20 of 99 Posts
Top