You could try looking through some very recent posts, or even using the search feature !!

http://www.benzworld.org/forums/r129-sl-class/1511244-vacuum-lines-replaced-egr-cleaned-icv.html

 

Why did you think i opened a new thread? Maybe because i couldn't find anything with the search function. Could be i used the wrong search string, but i couldn't find anything useful.
But thanks for the link!

 

I don't think that this relates to the other problems.
It is the first time that I am aware of this type.

Or maybe it is.
Be more specific what rpm are in Park/N?

You should have 500to 550 rpm in drive, give or take a little.

You could have a short somewhere that throws the computer out, and in
when you engage the drive?

Check for codes.

Then I would start checking the four pin engine temperature sensor with an OHM
meter, you should have at 20C about 600 ohms.
Check the ICV clean with carburetor cleaner.


Regards.
aam.

PS.
There is no need to vent frustration, we are here to help you.

 

reuzenkind/RedLiner,
Spring is here! It's time to take a deep breath, smell the flowers and go like hell! Albert (aam) and I are from Southern California. Perhaps you have heard of the place. Also known as The Land of Fruits and Nuts! We are a couple of helpful Nuts! Chill out!

I would like to know what your idle rpm is in neutral with a warm engine. If it is around 1000, Chances are it is a bad idle control valve. I was looking at about 1000 rpm in neutral in my car, but it would drop to 500-700 in drive. I had to stay on the brakes. Let off the brake and it would idle down the road at 1000 rpm. I replaced the ICV and saw immediate change to 500-600 in drive and 600-650 in neutral. Have it checked out.

 

Aam and Roadking, thank you for your replies. No hard feelings towards Redliner, but honoustly i couldn't fine anythin useful when i used the search function

I'll note down today the exact rpm's, and report them here.

Aam, do you think resetting the computer will help sorting the short out that throws the computer out? Because i need to reset the computer anyway, because of the SRS light that stays burning after an very empty battery. What i've read, it can be caused of a low voltage error stored in the computer.

 

420 SEL changed Idle control valve, Changed Idle control Module, Changed computer.
Changed cracked air delivery hose. And still have a high idle Problem. Newbie S.O.S

 

It's not just reuzenkind's query (we're cool BTW) It just seems that this topic just keeps recurring!
I can picture so many threads on this issue with photos of idle valves and aam explaining what to do :bowdown:

This thread will soon disappear down the topic list until the next time someone asks the same, or a similar question.
If I had half a day free, I would filter all 'Idle' topics into one topic group. (any volunteers )

 

Rainman 420sel year? you are forgetting that a bad wire or vacuum leaks can give you the same problems.
I am against of replacing good parts.
I rather trouble shoot.

James I understand that it is over and over the same things, which makes a lot of challenging of your work of shorting the posts but I sometimes try to give a short answer.
Move them along...............

Like Mike said if your rpm is less then 1000 shifting it in drive could go to 600-700
that is why I asked for specifics.

Regards.
aam.

 

Since my post yesterday, I purchased alldatadiy. I learned that the Throttle Valve Switch is stuck in the open position. I also learned that the valve switch is located at the front of the engine on the drives side in the area of the cold start valve and the idle control valve. Two size 10 screws hold the connection in place. Disconnect, clean or replace. I am currently waiting for my replacement part to arrive in the mail.

 

LOL - hey Rainman fill in your data - year model etc in the profile - :thumbsup: so the rest can figure out what your working on ....

 

Aam I've made some pictures of the idle rpm's.

Warm engine after highway

D


P

After a short ride downtown


D


P

Maybe you can say something from these photos?

 

Read my post again.
1. Four pin sensor, or wiring.
Computer thinks the engine is cold, = high/low rpm

2. You may have to replace the ICV.
Could have intermittent problems.
This valve is not moving on/off, it vibrates.

An other member had the same problem a few weeks a go, the ICV was doing it.
I have posted...... I don't even know how many times on this kind of problem.
I think with success. Haha.
Look the problem post by the member infra.

Do an advance CK.

Regards.
aam.

 

Sorry Aam, i thought you needed the RPM's to be able to specify the problem further. But i will try the things you mentioned, and will update when i made some progress.

Thanks!

 

Yes, I filled in 91 420SEL two days ago.

 

Guys..............
You must understand that we are trying very hard to help you, but we don't have physical ways to trouble shoot the problems that we all are facing.

If you remember that when I had my engine ticking, I was all alone...............
OK, I repaired it but we are all alone at the end.

I understand your frustration Rainman...........
I see that you have replaced the hoses, ICV, computer, etc.
And still you have high rpm.

Can be bad wires/connections, air leaks.
If the electrical checks OK, then you have air leaking in somehow.
Remember that the ICV is nothing more then a controlled leak.

All the parts that you have replaced where they new?
Also sometimes they can be defective.

Reuz.....
Yes the pictures do help......... It would help more if we can also see the temperature gauge, and have an idea of the outside temperature.

For example I am in California temp. is low 50F and up, other places below zero.
Please remember that you also must do the tests, if not we are running in circles.

Regards.
aam.

 

When I had the high idle issue, my indy swapped breather hoses (T-shaped), gaskets for manifold, air flow meter and injectors. After the replacement, high idle (2000rpm) dropped to 1000rpm at P and N. Now it stays 600-650 at D for my '92 SL.

 

Thank you.
And that's what I am talking about Vacuum leaks, the whole thing not just a hose here and there.

Regards.
aam.

 

Now you may want to examine your throttle valve switch. There are several components that effect the idle speed. This one cost an average of $30.00. knowledge of/and usage of a multi-meter is required to replace this part accurately.

 

Just an hint of "easy fix" of high rpm idle.

By accident I broke the adjusting screw for the trottle wire, and I order a new one for replacement. AND...... my high idle rpm was just normal, just like that. ( from 1000-1100 to 700 in P and N )
Maybe the wire was tuned too hard so the trottle not was realy closed or the wire has been damaged some where, but now everything is normal.

Just sharing the easy fix hint with you.

Knut

 

from you photos, pls check at

-air flow, make sure it's adjust correctly, DIY by volt meter or basicly pull the plug out at idle to check if any idle speed is moving

-Idle speed control valve, u can clean and might help for a little or pull the plug out to test at idle speed

-a screw that adjust the close/open of the throttle then send the signal that located under the in take below the air flow, need to adjust

and a few parts need to check, please letting me know if I can help

k@koranan.com

 

91 500SL - Idle Adjustment

i have a 1991 mercedes 500sl i know i have to push down on the idle screw and turn but how far do i push down thanks in advance

 

This is a virgin territory, MB doesn't want you to mess with.
But any ways go explore.
May be you all ready broke through their first defense.
The cap?
Most likely you did that's why you are asking how long, is long?

In there is a female Allen screw waiting like a Princes...
This is the security female head screw that you can't see.

How deep is/ long is needed?
Man these are tough questions... Haha.

Don't worry the long side of a long 3mm Allen tool is long enough.
They also sell extra long... special adjusting tools.

You push the upper male 3mm Allen Prince, down.... this must engage the lower female Princes.. head .
Then you adjust, let them Rock?
The slower you make your moves the better.

OK, I will not go more in details after all, you are new.
Welcome to the forum.

Regards,
aam.

 

aam thanks for your help ive made the adjustment when i start the car my rpm rise to about 1200 then drops down to about 600 within 2seconds and i look at my muffler and see black smoke also when car is cold has a rough start any suggestions thank for your help

 

The idler adjusting screw should be treated with caution and a note made of how much it is turned so it can be put back to where it was. It is unlikely that this would be the cause of a rough idle and will possibly just exaggerate the problem. the screw is just a fine tuner if everything is running ok.
good rev range appears to be 500-550 in D and 650ish in P.

Checking all the basics first will often cure most problems i.e. any air/vaccum leaks especially at the idler-injection hose connectors, ignition plugs, leads, caps & rotors (the favourite ) make sure all these are checked and eliminated before throwing money at the problem.

Bin Der Don Dat :crybaby2:

 

Check my earlier posts - might help....

But your talking with the experts now!!

Throw in BobTerry and you got the motherlode in info on this.

Since you have already adjusted the screw- 3 THINGS

1. FIRST OF ALL TINY ADJUSTMENTS - IT IS POSSIBLE TO SPIN THAT SCREW OUT Completely ALTHOUGH UNLIKELY YOU WILL THEN NEED TO REMOVE THE FUEL DISTRIBUTER- Not a DIY project!!

2. That said Go spend $49 dollars on a "duty cycle" multimeter SEARs #

3. Write down the process and "digest it"

Here goes::

HOLD on Im not working now Ill take some pix to show you EXACTLY how to set this according to BobTerry who personally came by and showed me this technique

Ill be back in 45mins

 

OK here goes

Take notes..

The pix are attached- its actually very simple
This probably will NOT fix your probs, but you will need to do it now that you have alreay mis-adjusted your idle-

Personally I think its either Caps, Plugs, and rotors-

See the stickies in this forum

The connectoris located next to the EZL ign packon drivers side-It is the round 16 pin as shown in the pix

Take the RED lead of the multimeter and place it in the #2 duty port.
Take the BLACK lead of the multimeter and place it in the #3 duty port.

WE'RE LOOKING FOR THE '50' READING ON THE METER-

SPEED UP THE ENGINE-
RUN AT IDLErepeat the process several times

HIGHER THAN 50 IS rich
LOWER THAN 50 IS lean

WE'RE LOOKING FOR THE '50' READING ON THE METER-

i Forgot whether clockwise is rich I think !!

Anyone Chime in her at any time and

GOOD LUCK !!!

 

What happened to the PIX ??

Gotta shrink the pix more


BRB

 

Thesze should go

These should work