1971 280sl runs terrible at / off idle

[marcski1971280sl]

Good day. I have a 1971 280sl. I had to replace the distributor #0-231-116-051, and since I did so I have experienced a horrific idle / acceleration. I went through the forums here prior to doing so to be sure it was as basic as it has been on the many I have done over the years. On a side note, I at the same time stupidly gave it a complete tune up with new filters, plugs, plug wires and I say stupidly as now I can't be certain whether the issue is the distributor install or possibly a tune up component causing the issue.  The dwell is 36 degrees, timing set at 30 degrees @ 3000 rpm. I replaced the distributor as it was making a loud noise, I took it out of car and tried turning it and it would loudly click and you could feel it sticking hard as you tried to rotate it, unlike any I've seen before.  I have been through the install process multiple times thinking I messed it up somehow, but with the off set where it engages into the drive kinda hard to do. If I set the idle timing to where it belongs it runs like manure, I brought the rpms up to 3000 and set the timing at 30 degrees and once it came back down to idle it was damned near chugging, so I brought it out for a ride anyway just to see -- it ran awfully in lower rpm range but then once it got to 2000 rpm or so took off quite nicely. I do not want to chase my tail on this, but have been trying to go through posts to see if there was a methodical way to sort it out. I am here asking for whatever help may be available. On a side note the eng # is 130-983-10-003095 I think it may be from an older model, didn't see anywhere in forum to enter it or look it up to confirm this fact though.  Any help is appreciated.

[teahead]

Hm...you have a 1971 USA model?

Shouldn't you have an 062 distributor?  Or 067?

https://www.sl113.org/wiki/Electrical/Distributor


What kind of throttle body do you have?

[Benz Dr.]

If you had the 051 distributor you should set your timing to 38 degrees BTDC. 30 degrees is how much the distributor advances and you also have to add 8 degrees to that for idle timing.

Sounds like someone used the wrong screw to hold the condenser in place. If this screw is too long it will hit the arms that hold the flyweight springs and bend them badly. Your original distributor can be repaired.

[marcski1971280sl]

It is a German model, and the distributor # ends in 051 - That is my question regarding the engine, I think it was swapped out. That should not make a difference as the only change would be setting idle timing correct? Which is a moot point. I will try to set timing at 38 degrees as opposed to the 30 I have it at now. But am not hopeful that will cure it, but I have been surprised before.  Thank you for your reply.

[marcski1971280sl]

I have the throttle body without the "US" dashpot at the throttle body for deceleration, I believe that makes it a non US model?  Would the distributor make a difference outside of the base idle timing setting? Wouldn't setting the timing at 3000 rpm be the "base" setting once done? I have set it removing and plugging the vacuum advance unit and leaving it attached. Both ways the idle is poor to say the least and it has a wicked "bog" as you accelerate from a stop. I can adjust the timing so its ok at idle but then the idle itself is high, I want to try and set it up properly and not to some crazy setting just to make it run properly. I sure as heck do not want to damage the engine in the process. Thank you for your reply.

[teahead]

Well...I'm a Pagoda noob, so I'll just parrot what others have said.

Do the linkage adjustment.  Check your spark plugs to see ifyou're running rich or lean.

Wicked bog?  That just started or you always had that?

Idle high?  Turn down the air screw, and check your vacuum.  YOu want I think 15 psi.

[Pawel66]

Marc, I am not a mechanic, so please do not trust me.
I also do not know how fluent/knowledgeable you are in mechanics. But I have been through the pains you are describing and got over them with help from the Members here. My first learning was to abandone "shooting from the hip" diagnosis and start more organized approach - saved lots of time, money and frustration.


You are a Full Member so you have access to what you need. If I were you, I would:
1. Check the throttle body if it is advance or retard and if it fits your distributor - someone was doing some mods there. You have the info in Technical Manual.
2. Check if you have copper core leads, no resistance connectors (other than 1k plug connectors) and no resistance plugs.
3. May consider using a new set of plugs for further work.
4. Inspect 051 as Benz Dr. is advising
5. Set the timing as Benz Dr. is saying, everythign connected. Following his advise I have 8BTDC at idle and 38 at 3k rpm. Set the dwell.
6. Do the proper linkage tour, really thorough. No shortcuts.
7. On your rough idle do the basic split linkage test - then you will know where you are in essence on idle mixture and further adjustments may start from there. If your rough idle is hight, try to get it lower with the air screw (like teahead is saying) then do the split linkage test.

On idle adjustment - I thought I got the idea some time ago, but recently I am learning there is more to it, so you may want to seek advise here on the forum when you get to this point.

I had serious engine hesitatin on acceleration and it was late timing and too rich mixture. The only non-standard thing I did was to switch to 123, but that is not necessary.

[Shvegel]

Just realized Dan (Benz Dr) beat me to it:
The clicking sounds familiar.  I am guessing when you installed the condenser the screw you used was too long and protruded into the distributor and scrambled the entire centrifugal advance section to mush.  I did that to mine.  remove the condenser screw and try to turn it.  If it turns free you will have to pull the distributor apart and see what the advance setup looks like.  pull the condensor, vacuum can and the 2 screws that hold the cap clamps (No need to pull the screw with the little spring plate). Keep track of which clamp goes where if they are different.  I think your's are both the same but some have a little tab at the top to locate the distributor cap.  Gently pry up the plate the points mount to and see if you can see anything bent or broken.  I probably have parts I can send if you need them.  Gratis.


Only US spec 70-71s had transistor ignition so only they got the aluminum body 062 and 067.  they are tough ones to come by($$$).

[marcski1971280sl]

I have the throttle body without the "US" dashpot at the throttle body for deceleration, I believe that makes it a non US model? The distributor is a new one, # 0-231-116-051, dwell is 38 degrees timing at 3000 rpm is 30 degrees. Thank you for your reply.

[marcski1971280sl]

I have a German model I believe, no dash pot at throttle body. Thank you for your reply.

[marcski1971280sl]

Could be, but the distributor is new now. I am thinking now possibly wrong wires, I will ohm them and see, they are not solid core I know that much. There is a vicious bog at idle until like 2000 or so rpm. Thank you for your reply.

[Pawel66]

I am very sorry if I am leading you the wrong way.

I just thought that if your engine was swapped, it might have had the vacuum advance throttle body. The distributor you replaced (we do not know the type) might have been vacuum advance distributor.

051 that you installed is a vacuum retard distributor. It needs vacuum retard throttle body.

Please take a look here. It will take you 5 minutes to determine if you have throttle body matching the distributor: https://www.sl113.org/wiki/Fuel/Throttle

For 051 you need vacuum retard throttle body.

If they are a match, you will look for issues elsewhere.

I am not sure if it matters if the throttle body has a dash and if it is US or Euro. What matters is where the vacuume line is taken from.

[Shvegel]

Marc,
I knew your distributor was correct for your car if it is a Euro spec car.  I was only pointing out that ONLY the US spec cars got the 062 and 067 units designed for Transistor ignition. Youe engine number prefix is correct for your car.  130(M130 engine type) 983 denotes 280SL as opposed to sedan, 10 for manual transmission then the serial number. 

If you don't have these black relays behind the battery you have a Euro spec 280.

[marcski1971280sl]

Ok, so this car is an automatic not a manual transmission. I really think wrong engine, correct for model etc... but not original to the car. Question is what year is the engine and tune up specs should be???  Thank you for your replay.

[MikeSimon]

There are a ton of little differences between a European/German car and a US model and, depending what was done when someone "federalized" it, you should be able to find out which it is.
The engine serial number of 3095 indicates it is an early 280, most probably not original to a 1971 (late 1970 built) 280SL
Question for Pat: Does the "10" in the engine serial number really indicate "manual" transmission?? I though that ID was only in the chassis number. Engines are usually completed and numbered before mated to a chassis and I would think they did not know what tranny the engine would come together with at that point.

[Shvegel]

Mike,
According to our own technical manual:
"The seventh digit identifies
                                           1          left-hand drive
                                           2          right-hand drive
             The eighth digit identifies
                                           0          manual transmission
                                           2          automatic transmission"
I believe some of the earlier engines had crankshafts that were not drilled for the clutch pilot bearing and the flywheel or flex plate was balanced with the crankshaft thereby making it a dedicated manual or automatic engine.  The low number is I think indicative of how few manual transmission 280's there were.

[marcski1971280sl]

 Oh, that is good to know. I will verify whether or not those relays are there, been under that hood so much that I really can't recall right now. If I could get the year of the engine I could verify tune up specs to be sure I'm not trying to find something that some simple tuning or a different tune up part may cure. - Thank you for your reply.

[marcski1971280sl]

The vac line to distributor goes directly to a nipple mounted on the underside of the throttle body itself. Does not connect to anything, meaning dashpot etc. - Thank you for your reply

[Benz Dr.]

Mike,
According to our own technical manual:
"The seventh digit identifies
                                           1          left-hand drive
                                           2          right-hand drive
             The eighth digit identifies
                                           0          manual transmission
                                           2          automatic transmission"
I believe some of the earlier engines had crankshafts that were not drilled for the clutch pilot bearing and the flywheel or flex plate was balanced with the crankshaft thereby making it a dedicated manual or automatic engine.  The low number is I think indicative of how few manual transmission 280's there were.

Standard and auto engines are more similar than they are different - at least in terms of the long block. The crank shaft's are the same except for the dowel pin that locates the flywheel or flex plate. The dowel pins are different lengths. All cranks were drilled at the back end which holds the pilot bearing for the input shaft on a standard or the nose of the torque converter for an auto.

The real differences are more on the engine ancillaries like IP, bell housing, drive shaft, radiator, neutral switch, etc.

[marcski1971280sl]

Makes sense from a manufacturing stand point for sure - Thank you for the info.

[marcski1971280sl]

Okay  some up to date info --->

There are no relays by the battery so that makes it a German spec'd engine

Coil primary resistance is 600 ohms - Secondary is 3500 ohms

Plug wires are all pretty much 700 ohms - non solid core type

Plugs are Bosch R6 - WR7DC - I think they are resister type - which means wrong ones?

Timing at 700 rpm is 9 degrees with 10 inches of manifold vacuum - to get 15 inches at idle had to put timing at 45 degrees

Timing at 3000 rpm is 30 degrees

Plugs all look like they just came out of the wrapper - like car is running lean - I think I need plug wires and the correct plugs?

Any thoughts on this is greatly appreciated.

[Benz Dr.]

What coil are you using? The standard black coil, the hotter red coil, or something else? Even though you are using fairly cool spark plugs, they're kind of on lean side. How many miles are on your plugs?

Based on what you are running for initial timing, I think your distributor isn't advancing properly - you should have 39 degrees full advance and not 30. What is your distributor number?

[Benz Dr.]

What do you mean by '' non solid core type '' ignition wires?  If they're carbon core that will be your problem.

[marcski1971280sl]

It's a silver coil I will get #'s off of it, it does have a resistor feeding it. And they are the modern type flexible carbon core style plug wires. There are very low miles on the plugs as I installed them a few weeks ago, same with the plugs and distributor. Thank you for your reply.

[Benz Dr.]

It's a silver coil I will get #'s off of it, it does have a resistor feeding it. And they are the modern type flexible carbon core style plug wires. There are very low miles on the plugs as I installed them a few weeks ago, same with the plugs and distributor. Thank you for your reply.

OK, throw those wires in the trash can and get a full set of metal core wires. That is your problem.