1984 W123 230CE (or 230E I guess) Cold idle speed question

[Rob. Smith]

Not sure I have a problem, but when the car is cold (1st start in the
AM), it idles too slowly and is very 'juddery'. Putting it in D helps
a little (as the vacuum controlled ignition retard function is turned
aff), but its still too slow when drive is taken up (at idle). It
drives fine, so I feel the warm up regulator is richening it up OK.

I have changed the electrically heated Aux air valve for another (not
a new one however), but the effect is the same.

When the engine warms through, the idle speed is ~800 and nice and
smooth. Also the CO content is spot on at this point too.

Can anyone tell me what their late 123 series 230E (or CE) does (rpm
wise etc) when cold at idle?

Any suggestions about what to check?


Cheers... Rob.

[Roland Franzius]

Post by Rob. Smith
Not sure I have a problem, but when the car is cold (1st start in the
AM), it idles too slowly and is very 'juddery'. Putting it in D helps
a little (as the vacuum controlled ignition retard function is turned
aff), but its still too slow when drive is taken up (at idle). It
drives fine, so I feel the warm up regulator is richening it up OK.
I have changed the electrically heated Aux air valve for another (not
a new one however), but the effect is the same.
When the engine warms through, the idle speed is ~800 and nice and
smooth. Also the CO content is spot on at this point too.
Can anyone tell me what their late 123 series 230E (or CE) does (rpm
wise etc) when cold at idle?
Any suggestions about what to check?

Have you checked the engine house vacuum? It is used to drive control
hoses and cold idling is bad if the crankshaft ring gasket is defective
or the vacuum hose from camshaft cover to intake manifold is closed by
oil debris.

[Rob. Smith]

Post by Roland Franzius

Post by Rob. Smith
Not sure I have a problem, but when the car is cold (1st start in the
AM), it idles too slowly and is very 'juddery'. Putting it in D helps
a little (as the vacuum controlled ignition retard function is turned
aff), but its still too slow when drive is taken up (at idle). It
drives fine, so I feel the warm up regulator is richening it up OK.
I have changed the electrically heated Aux air valve for another (not
a new one however), but the effect is the same.
When the engine warms through, the idle speed is ~800 and nice and
smooth. Also the CO content is spot on at this point too.
Can anyone tell me what their late 123 series 230E (or CE) does (rpm
wise etc) when cold at idle?
Any suggestions about what to check?

Have you checked the engine house vacuum? It is used to drive control
hoses and cold idling is bad if the crankshaft ring gasket is defective
or the vacuum hose from camshaft cover to intake manifold is closed by
oil debris.

Thanks for the reply

I am confident I have good vacuum. The 'economy' vacuum gauge reads
good, and the vacuum retard system operates to the full extent at
idle.

When you talk of the 'crankshaft ring gasket', I am not sure what you
mean. Do you mean the gasket under the oil filler cap, or are you
concerned about blow by from the piston rings?

As for the crank case ventilation system, you are correct in that I
have not yet checked that. I used to own a W123 280E, and that had a
blocked (oil debris) crank case vent. That would cause oil to be blown
out of the dipstick tube till I fixed it.

One thing I can tell you is that the idle bypass screw (idle speed
screw) had to be unscrewed so much that there was a loud hissing noise
from the air passing through it to make the engine idle properly. I
have had to open the throttle butterfly flap slightly (adjust the
throttle butterfly stop screw) to allow me to close (screw in) the
idle bypass screw to reduce the noise from the idle speed screw area.
This is porbably not what I should have done, but I can easily return
it back to original.

Thinking about the evidence I have, and your points, I think that I
should make a full investigation of the crank case vent pipes and idle
control pipework.

Cheers... Rob.

[Roland Franzius]

Post by Rob. Smith

Post by Roland Franzius

Post by Rob. Smith
Not sure I have a problem, but when the car is cold (1st start in the
AM), it idles too slowly and is very 'juddery'. Putting it in D helps
a little (as the vacuum controlled ignition retard function is turned
aff), but its still too slow when drive is taken up (at idle). It
drives fine, so I feel the warm up regulator is richening it up OK.
I have changed the electrically heated Aux air valve for another (not
a new one however), but the effect is the same.
When the engine warms through, the idle speed is ~800 and nice and
smooth. Also the CO content is spot on at this point too.
Can anyone tell me what their late 123 series 230E (or CE) does (rpm
wise etc) when cold at idle?
Any suggestions about what to check?

Have you checked the engine house vacuum? It is used to drive control
hoses and cold idling is bad if the crankshaft ring gasket is defective
or the vacuum hose from camshaft cover to intake manifold is closed by
oil debris.

Thanks for the reply
I am confident I have good vacuum. The 'economy' vacuum gauge reads
good, and the vacuum retard system operates to the full extent at
idle.
When you talk of the 'crankshaft ring gasket', I am not sure what you
mean. Do you mean the gasket under the oil filler cap, or are you
concerned about blow by from the piston rings?
As for the crank case ventilation system, you are correct in that I
have not yet checked that. I used to own a W123 280E, and that had a
blocked (oil debris) crank case vent. That would cause oil to be blown
out of the dipstick tube till I fixed it.
One thing I can tell you is that the idle bypass screw (idle speed
screw) had to be unscrewed so much that there was a loud hissing noise
from the air passing through it to make the engine idle properly. I
have had to open the throttle butterfly flap slightly (adjust the
throttle butterfly stop screw) to allow me to close (screw in) the
idle bypass screw to reduce the noise from the idle speed screw area.
This is porbably not what I should have done, but I can easily return
it back to original.
Thinking about the evidence I have, and your points, I think that I
should make a full investigation of the crank case vent pipes and idle
control pipework.

As far as I see on detailu.ru the 230E engine M102 has the same cold
start fuel pressure regulator as I know it from the M110 of the 280E/SE.

It is a little block at the left down on surface the crankcase. It is
an electrically heated themostat and intake vacuum membrane regulated
fuel bypass working for the first five minutes after cold start.

My 280E was - well not quite - handicapped by a hole in the control
membrane between fuel line and intake manifold. The result was an
extreme fuel consumption of around 25l/100km.

Made it a very cheap buy and a Porsche like booster when I purchased it
in 1989. After fix that W123 280E was the best MB car/engine of all times.