bad idle 190e

[190emerc]

I have a 190e 2.0 on a 'H' plate, its a 1991 car that A1 apart from the dodgey idle!
It starts fine but idles about 1700-1800rpm whilst in park or neutral which is too fast, put it into drive and it drops to approx 1000 rpm, again slightly too fast.
When it gets hot the problems really start, it starts to idles from 1800 to 800 rpm and wants to die eventually.
I have changed the rota arm and dizzy cap, the previous owner apparently had the fuel distributer changed along with the fuel filter all to no avail.
I also changed the idle speed control valve again to no avail!! fortunately the shop took it back which is good as it was £120.

If anyone has any ideas i would be really gratefull

 

[mattkh]

Hi
Clean the throttle.

 

[Number_Cruncher]

Here's a response I gave to the OP "In another place"

-------------8<-----------

It sounds like either the throttle plate is set too far open, or there's an air leak allowing air to bypass the throttle.

There will be a method to set up the base throttle position - sorry, I don't know it off the top of my head.

It will be along the lines of;

- clean the throttle body and throttle plate
- slacken the throttle position switch adjustment
- fully slacken the throttle stop screw - also fully slacken the cable
- snap the throttle open, and allow it to shut with the spring (the plate should lock into the body)
- screw in the throttle stop screw until the throttle plate bumps free of the bore
- tighten another quarter of a turn, and lock the locknut
- reset the throttle position switch
- reset the throttle cable

It will be worth asking on either mbclub or mercedesclub.org to find the correct method.

If there is either too much throttle opening, or a major leak, the idle speed controller will not be able to compensate - it's only meant to control/compensate for small changes

-------------8<-----------

What's the right way to set the basic throttle position on these engines?

 

[television]

If this car has a rotary idle valve,it will not have any idle setting screw

 

[Number_Cruncher]

>>If this car has a rotary idle valve,it will not have any idle setting screw

No, that's right, but there will still be an adjustable throttle stop - which is set at the factory and normally shouldn't be touched, because, as you correctly point out, idle speed control is done by the rotary actuator.

There will be a throttle stop screw to enable the throttle's basic position to be set - to allow for production tolerances on both the throttle bore diameter, and the throttle plate size. The usual aim of this production setting is to have the throttle as close to closed as possible without the plate binding in the bore.

Normally, this production throttle stop is sealed - either with plastic caps, or with paint - to dissuade the Kamasa socket set brigade - however, if they do mistakenly use it to mis-adjust the idle, it really mucks up the idle speed correction via the rotary air valve - hence the resetting procedure, which makes no mention of adjusting to obtain a particular idling speed.

 

[190emerc]

as advised i will try this.....but does anyone have a blow by blow account of how to do this??? i am a mercedes novice and could do with taking through it step by step and number cruncer suggested i may post on here to see if anyone has the correct procedure for setting the base throttle position,

Many thanks to all helpers!

 

[television]

All of what I have says that the idle is electronically controlled

 

[Number_Cruncher]

All of what I have says that the idle is electronically controlled

Yes - the OP has changed the rotary actuator - to no avail.

On the other forum, I asked about the idle switch on the throttle, which the OP has checked, and has said is OK.

Malcolm - to be clear, the base throttle adjustment has nothing to do with setting the idle speed - what it does do is to set the throttle near closed, to allow the idle speed to be controlled by the rotary idle actuator. If some fool comes along and tries to adjust the throttle base position thinking that they will adjust the idle speed, all they end up doing is mucking up the idle speed control via the rotary idle actuator.

What I'm trying to find for the OP is the correct way to check and re-set this basic throttle setting - to allow the rotary idle actuator to be in its operating range.

Please forgive the non-MB thread drift - On the Vauxhall Cavaliers with Bosch Motronic and rotary idle actuators, alas the stop screw for base throttle setting was a bit too accessible to the Kamasa socket set brigade, and the number of maladjusted throttle bodies on cars with electronic idle speed control completely messed up was sadly epidemic in the early 90's!

 

[roofless]

it could be the regeneration valve stuck open No5 in the link http://www.detali.ru/cat/oem_mb2.as...717.411412&CT=M&cat=504&SID=14&SGR=120&SGN=06 it's easy to check just block the pipe at the engine side & see if it runs even

 

[190emerc]

will have a look at the valve tomorrow.....where will it be situated on the engine and what am i looking for (what does the valve look like, big small?). i am a novice merc owner!!! so any help is gratefully appreciated

 

[roofless]

will have a look at the valve tomorrow.....where will it be situated on the engine and what am i looking for (what does the valve look like, big small?). i am a novice merc owner!!! so any help is gratefully appreciated

this is the one on my e220 w124 i would think it will look something like it if you pull the black pipe off that will go from the valve to the throttle body & blank it off

 

[mattkh]

When it gets hot the problems really start,

Hi
Read the post again.
The other thing to do is to change the engine temperature sensor used by the idle stabilisation system.