560SL.. rough idle/shaking,then stalls...

[ioang26]

Hello everyone,

Iam new here and just bought 1986 Mercedes 560SL which has been sitting for the past 3+ years and now when it is started(cold starts immediately) has a rough/shaking idle and after it warms up a little stalls.When I get to drive it ,drives fine but as soon as I slow down and remove my foot from the gas it stalls and dies.I need to crank it a few times to start again and that will repeat.
Although the car starts right away when it is cold but still has some shaking .The new spark plugs are all black and were wet when I got the car .
Also,the odometer and the tachometer don't work only the speedometer works.

Any advise and help would be greatly appreciate it!

[ioang26]

Anyone?

[tecqboy]

Well, the fuel systems / ignition systems on these cars are particularly complex. And there are many variations on them over the years. It could be almost anything or a number of things combined, especially after sitting so long un-driven. Just the old gas in the system could have sludged things up. Old vacuum hoses may be cracked. Electrical connections may be corroded. Sensors may be failed. Filters may be plugged. If you are not familiar with Mercedes, then the best advice I can offer you is find a good mechanic who is. If the car was otherwise maintained well, it need not be expensive to get it running well again.

[meltedpanda]

so many things, btu since she has been sitting start with fuel delivery ( your plug condition may indicate rich burning)
Injectors clean with good spray pattern?
air plate on intake free to move and clean andjusted?
Any vacuum leaks?
Fuel filter and lines clean?

I suggest getting the book

How to Tune and Modify Bosch Fuel Injection, by Ben Watson

[ioang26]

Here is the history of the car.
It has been sitting in a garage for 3+ years,well maintained before that.
Some shop before me did the following to it:fuel pump replaced,new spark plug wires, new NGK R BPR 5ES spark plugs,new ignition distributor,an used fuel distributor installed.

I have done the following so far - new fuel filter,drained the fuel and added new with fuel additive, cleaned the fuel lines, air sensor plate moves like there is a spring under it but it is not stuck.

When cold - as soon as I turn the key starts and then idles rough and shakes,when warms up to the normal temperature would stay sometime idle low and then would stall.When stalls and try to start it right up would take a few cranks and gas pedal pressed to fire up.

I read some about the KE Jetronic system and have an idea how most of the stuff works but I am still new at this.

Where should I go from now?Any place to start checking first/

Thank you all!

[meltedpanda]

cold start issue/rough cold idle:
1)incorrect cold control pressure ( 16-24)
2)AAV not opening properly
3)Leaking cold start valve or not functioning
4)improperly adjusted airflow sensor
5)bad injectors /leaking injectors

if she has sat for 3 years, take the time to refurbish/replace injectors
Does the oil have a gas smell to it?

and you need to get a reading on fuel pressure and rest pressure
IMHO , The KE jet sytem may be the hardest to trouble shoot

[ioang26]

meltedpanda,

Yes, the oil when I got the car had a strong gas smell but I don't know how long it has been sitting with that oil either.
Today I replaced the old FD with a rebuilt one.The old one plunger when pushed would go and then would not come back after 5-10 seconds.Removed old injectors and tested the spray pattern and cleaned them,installed with new seals.
It is turn to replace the O2 sensor but I need some assistance since the wire goes somewhere inside.

[meltedpanda]

that smell may indicate leaking injectors or Cold start injector, you are on the right path!

[ioang26]

An update - today replaced the FD with a used one,new O2 sensor .
The car started right up and was running well... but after warmed up I noticed that the EHA is leaking but not from the "o"rings and the rpms went gradually down.I turned it off.
Now I am waiting on another EHA and Jetronic fuel pressure test kit.
I still can not find the culprit why the tach is not working.I put an extra ground but no results.Any suggestions?

[meltedpanda]

I think that tach signal is fed by an output from the EZL (electronic ignition control unit), unlike the older pulse from the distributor
May be a bad tach or bad signal or both

[ioang26]

Is the EZL located on the dirver's side under the fender next to the turn signal area?
How should I test it?

[meltedpanda]

not easy to test or repair, look here
Anyone opened a failed EZL before? - Mercedes-Benz Forum

[KCM]

Originally Posted by ioang26

Also,the odometer and the tachometer don't work only the speedometer works.

As for the odometer, it is most likely one of the plastic gears that drive it on the speedometer head. There is one small gear in particular that goes bad. Here is a site with some very good instructions on replacing it:

Odometer Gears - Mercedes-Benz - SL (107) 81-89

I just replaced the small gear on mine and it was not a major job (once the instrument cluster is out). Bought the gear off Ebay.

As for the tach, I would not jump the gun on the EZL. Might just be something simple. Don't have an electrical schematic handy to look at right now.

The EHA leakage must be a common problem. I've had to replace that too.

[meltedpanda]

True. I only mentioned the EZL as a possibility. Rule out the simple first.

[ioang26]

Well...I fixed the the odometer .There were 2 broken gears but the tacho is still a mystery because even the clock works , everything on the cluster works.
Also, today I replaced the EHA and there is no leak, but now the car would not even start.What is the problem?
Did I do something wrong?Please, help!