ROUGH IDLE, IDLE CONTROL UNIT LOCATION, TIMING & RPM

[verdejor]

1981 380SEL Euro, 8cyl

I had to set my car to 5degrees Before TDC (per manual), I can't get it to adjust to that, I can only get it to go to 3.5-4 BTDC, Distributor won't turn any more,

RPM adjusted to spec using idle air control screw (500RPM, tried 650)

I tried playing a little with the fuel mixture screw (car turns on fine, it still has some black smoke when accelerated)

any clarification on how to used the pins on the computer diagnosing circle by fenderwell please...
I connect with voltmeter to pins 3 & 2for ground and only get reading of zero, is idle control unit bad? (battery reads 14.63volts)

this vehicle does not have electronic idle control VALVE. It is a Euro model

I ALSO don't have a oil temp sensor.
Can't locate idle control unit, looked under dash everywhere, looked under hood by cowl also. any help much appreciated!!

thanks again to all!

any feedback on my rough idle?
pls let me know something.

the only 2 "boxes under the pass side were the AC Temp. control unit (000-822-0903) and AC Blower control unit (000-822-1103)

thanks everyone!!!!

I will be replacing the following this weekend:


FUEL PUMP: It is humming some.
FUEL ACCUMULATOR: Just in case
FUEL FILTER: Has been changed
FUEL FILTER IN TANK: Just in case
TIMING CHAIN: It is double row, I checked my timing with the light and it is jumping back and forth some. I pulled a valve cover and it seems loose to me, not taking risks.

HAVE CHANGED:
FUEL INJECTORS
AIR FILTER
BELTS
OIL FILTER
OIL PRESSURE SWITCH
DISTRIBUTOR CAR, ROTOR, WIRES & PLUGS + IGNITION COIL
ENGINE SHOCK DAMPERS AND ENGINE MOUNTS
COOLING FAN SENSOR
ALL FUSES (NOT RELAYS)

ANYTHING I missed?

I checked vaccuum hoses for leaks...

[NordRhein]

this vehicle does not have electronic idle control VALVE. ....Can't locate idle control unit,

If it doesn't have an idle control valve then why would it have a controller? Very early Euros did not have idle speed stabilization - and FWIW your car is more reliable without it. Just set hot idle speed with the air screw and you are done with that.
As for the computer socket - it may NOT be a computerized car! Very early Euros had NO computer, if there is no wire on the Fuel Distributor for the electric bypass valve then there is no computer. The socket is merely a convenient place to read the crank position sensor - ignore it.
A rough idle is fouled plugs, fouled injectors, bad ignition or vacuum leaks. Vacuum leaks INCLUDE the black rubber manifolds. As for black smoke that points to an out of adjustment cold start regulator.
If the distributor is at the end of it's travel then it must be removed and "slipped" a tooth on the drive gear. Just mark where the rotor is at rest and reinstall one tooth off. As you pull the distributor up the rotor will rotate as the gears unmesh. That's why you need to mark the starting position.
Lastly this car does not have an oil temp sensor. If it makes you feel any better newer Mercedes cars have even gotrten rid of the oil PRESSURE gauge. Mercedes wants it's customers to be uniformed about what the engine is doing.

[verdejor]

NORDRHEIN,

You know too much.. first to answer and know more than anyone I have asked so far...
people just read the post, critizise, but no real knowledge is "absorbed" by most. [:)]

No offense to those who read and don't reply, just those that critisize without a real knowledge or intent to help a fellow MB Owner regardless of year/make or model. [:(!]

As for black smoke that points to an out of adjustment cold start regulator:

how do I know if it's really out of adjustment?
just replace?
[V] Getting frustrated on this part:
If the distributor is at the end of it's travel then it must be removed and "slipped" a tooth on the drive gear. Just mark where the rotor is at rest and reinstall one tooth off. As you pull the distributor up the rotor will rotate as the gears unmesh. That's why you need to mark the starting position.

I'll have to do some more extensive research.. maybe my haynes manual says something (note: Haynes Manual doesn't have my year/make model.. argh!!)

I have been reading this also...
in case other members need it for mostly any make model year:
I'm sure everyone knows it, just trying to help us all improve..

http://mb.braingears.com/

[NordRhein]

It's fairly easy on an early car without a computer - reason - you don;t have a computer to fight with. Mixture is controlled by two things - the position of the main metering plunger in relation to the air metering plate (allen head screw in the FI tower) and the cold start regulator - NOTE - AND damper if equipped - it is installed in the CSR line at the passenger side base of the FI dist. But lots of black smoke is either the CSR affecting the main metering piston too much or the mixture is adjusted way way off. You can check the CSR by understanding how it works - when cold the orifice opens and it bypasses the metering piston, when hot the orifice closes and you rely ONLY on the relation between the metering plate and piston. So - remove the CSR and put it in the freezer. With the right size tubing you can blow into one side and hear air hiss on the other. Now apply 12V to the coil - the orifice should close.
As for the distributor it will become very apparent if you simply remove it for the first time. You will see the rotor rotate - mark it first! Pull/replace several times and you will see where the rotor winds up and will be able to tell where the next tooth is. Do this with the engine at TDC and you will also see the rotor line up with #1, and then be advanced. Note because you are only playing with the dist you cannot mechanically crash anything, the worst that can happen is the car won't start - in which case go back to TDC and realign, or it may backfire if you get it too far off - in which case go back to TDC and realign.

[verdejor]

shifting the rotor sounds dificult. got confused on the instructions..
as for CSR.. what exactly it stands for?
I think I'll just purchase a new one if cheap enough yeah? everything else new already might as well, take it off the "list of this that can go bad in the near future"

thanks for all the help.
I need to get the fuel mixture adjusted with a CO meter b4 I change it though...

[NordRhein]

CSR = cold start regulator. It has two gasoline pipes going to it, an electric cable and vacuum hose. They're not exactly cheap but it sits on the passenger side of the engine just next to the air cleaner. If you don't have a computer you can just lean for best idle and then drop it 50 or 100 RPM. 50 is recommended but to pass my emmissions with flying colors - remember no computer - I leaned to -100RPM.
As for adjusting the fuel mixture BEFORE you change it - that's a waste of money beyond just leaning it yourself. The reason is with black smoke the CSR is richening it too much and there is no guarantee it ever fully shuts off no matter how hot the engine gets - therefore it screws up the hot idle mixture too.

[MBZER]

.... fascinating thread .

[verdejor]

Is the "CSR" = Cold Start valve?
making sure we R on same page...

What should I do?
I really want this smoke to stop [B)]
I have a list of things to replace this week, should I add the CSR to the list of replacements?

thanks 4 the help..
I'm sure this thread one day will clear a lot of things..
I will summarize it and repost later after it is fixed. Learning a lot.

what's your opinion on removing the cats?
will a straight through mufflers suffice(magnaflow?) ? or will the car be LOUD?

Cold Start Valve Pic..:

[NordRhein]

No - R =regulator. The cold start valve is used to get the engine running. It only operates with the starter engaged. After that the cold start regulator takes over.
Cats on an early Euro are abominations. The ideal setup is true dual exhaust, saddlebag mufflers and resinator.

[verdejor]

what brand do you suggest for the exhaust setup you mention (brands maybe)...

So you are talking about the warm up regulator?
My primary language is english so I try to translate as much as possible...

how can I fix an out of adjustment cold start regulator? is it only a replace part.. could it be a bad connection (wires)?
what are my choices here...?