Idle Control Valve
 

Can someone help me with info abut the ICV? I've taken it off and cleaned it but when I look down the tube, the valve is open about 1/4 of the way. Have put 12v on it and doesn't move, doesn't seem to click or vibrate when it's fitted. I presume as it's a valve it should open and shut. How can I test it? Is the rest position closed, open or 1/4 way open?

My thinking is it has jammed and is stuck in a workable position. Does that make sense?

As I've changed everything else, no doubt I'll be changing the ICV too but would like to know one way or the other before I spend another weekend fannying about under the bonnet.

Symptoms, if you haven't guessed already, are intermittent rough idle/stalling at lights/surging/driving the wife mad

Have checked or changed fuel accumulator, injectors, plugs, dist cap and rotor,air sensor pot, vacuum hoses, OVP and Fuel Pump relays.

Some test info would help a lot.

cheers

idle
 

I too have rough idle at the moment... Might need to check O2 sensor, as well as vacuum leaks....

You might need to give a detailed description of your problem inorder for members to lend a hand...

cheers,

model
 

and year?

Hi, thanks for the response. Let me give you some more info, see if you can help.

Car's a 1987 300e manual, no catalytic converter so no lambda, or closed loop operation I guess. Haven't looked but doubt there's an O2 sensor either. 160,000 km. Bought it 8 months ago and these idling problems started after I replaced the fuel accumulator to cure a hot start problem. Injectors were replaced at same time. Have changed OVP, Fuel Pump and AC relays. Fuel pressure regulator looks newish.

The problems include fluctuating idle, stalling when decelerating to a stop, the very occasional momentary loss of power under acceleration. They appear intermittently, which is making it hard to figure out what is wrong.

The only parts I haven't changed yet are the idle control valve, which I believe is stuck, and the air sensor potentiometer, which I swapped and swapped back with another unit.

Hot start is fine, cold start was fine until yesterday when it started playing up. Takes two or three cranks and a tickle on the gas to bring it to life. This has been accompanied by the return of stalling problem, intermittent 500rpm low idle when warmed up, occasional fluctuating idle.

My mechanic, who actually works at the local dealership, comes round at weekends to tinker. His experience is with new models so its a lesson for him with KE equipped cars.

When we have the air filter box off, we watch the throttle plate occasionally deviate as the idle fluctuates. He adjusts the idle by fiddling with the mixture until it stabliises to around 750. Blips up then stablises again when AC or PS load is applied.

The ICV was cleaned and both hoses replaced - one was cracked - when I swapped out the pot. This cured the problems for a week but then they came back.

Swapped back the pot last weekend as thought unlikely to be at fault and focussed on ICV. Removed and reconnected and tried KOEO, no movement. Looking at the slide inside the unit, which appears worn BTW, it is open about 1/4 way.

There is power at the connector so would expect the valve to close, as per previous posts. As there's no movement I conclude that it is jammed and needs replacing, which is fine. At $90 I'm OK with that.

That said, would a jammed ICV cause the symptoms I'm experiencing?

If I replace with a new one, is it OK to adjust the idle with the mixture screw? I plan to try the tip of estimating the mixture using a squirt of carb cleaner. I presume that without the closed loop situation, checking the EHA current wouldn't help.

Of course in the perfect world, I'll change the ICV and everything will work perfectly without adjustment. So any tips on setting the idle and mixture without access to CO analysis would be fantastic.

TIA for your advice and info

The rough-idle-and-die is one of the most perplexing problems of the 300E. I gave up and sold mine.

It sounds like the idle valve is a culprit. Are you getting current to the valve, though?

Don't try to set the idle by farting around with the mixture. Since you don't have lambda, you can use the current flow to the EHA to set the mixture. Once you have a good idle system and the right mixture, the idle speed will take care of itself.

Lots of post on measuring EHA current, and your friend should be able to get the specs for your car.

Thanks for the quick reply. Have just bought a new ICV and seen how it responds to 12v - nothing like the one fitted to my car :) - so will fit that this weekend and keep my fingers crossed.

Yes, getting current to the ICV, 12v at KOEO, haven't tested with engine running though. From what I've learned in the vast tract of 300e idle posts, when the engine's running this should be 6v with a 50% duty cycle (not sure exactly what that means yet but no doubt I will shortly).

Will now go looking for EHA current info for adjusting the mixture. If anyone can post or point me in the right direction to find this info, be much appreciated.

mixture
 

http://www.landiss.com/mixture.htm

Good read...

cheers,

thanks fo that. Have had a read but it deals with engines which use a lambda controller, which mine doesn't have. Any tips on whether I can use the X11 tests to check the duty cycle anyway? I'm not sure how my injection system will adjust mixture itself if it doesn't have closed loop.

Guess what, it worked

On a more serious note, just like to document what happened in case it helps someone else.

Bought a new Idle Control Valve at lunchtime, read up on mixture adjustment and X11 testing in the link above and decided I'd have a go myself. Stopped at my local hardware store on the way home and bought a multimeter and long 3mm allen key.

Found the X11 and tested ports 2 and 3, not sure if it would work as my car doesn't have a Lambda valve. Anyway, reading was 2.9 volts against a battery voltage of 13.4, which by my calculation is a duty cycle of 78%. Tried adjusting the mixture 1/4 turn either way but with no discerible difference.

Took the air filter off, changed the ICV, noted that there was a 6v reading at KOEO, which I assume is default 50% cycle.

Anyway, started up and ran great. As I wasn't having any luck with the X11 test readings on mixture, went straight for the carb cleaner method, which worked a charm. Leaned the mixture right off until there was an increase of revs - about one whole turn, I guess - bolted everything back together and went out for a test run. Went like a dream, no hesitation, low idle stalling, rough idle. I am happy, happy, happy!

I reckon I should try the X11 signals again to see if the duty cycle has changed, but don't know how not having a lambda valve would affect this. Would also like to check the fluctuation in voltage on the ICV and maybe even explore the air sensor potentiometer settings with my new multimeter but i'll leave that until the next time I have to take the air filter housing off.

Which I sincerely hope is NEVER EVER AGAIN !!! :o

Many thanks for the help and suggestions from those who replied to my post and also to the many many previous posters who each have contributed a little more to my understanding of the K Jetronic fuel injection system. If there isn't a book about this extraordinary adventure, there certainly should be.

[QUOTE]Originally posted by simmo300e
[B]Thanks for the quick reply. Have just bought a new ICV and seen how it responds to 12v - nothing like the one fitted to my car :) - so will fit that this weekend and keep my fingers crossed.

Congratulation simmo300e I am happy you solved your problem.

Do yo still have the old ICV ?
If yes, would you mind trying some thing to improve knowlmedge of functionning of that device ( I od not have a bad one)?
There is a screw on the ICV under a seal, and without any voltage on the ICV , I would like to know if thurning that screw clokwise increases opening or closing of the shutter.

in advance many thanks for your help

Sure, I'll give it a go. have to warn you though that the shutter in the valve ain't moving at all, even when I jammed a screwdriver down there and tried to shift it.

Thanks for trying simmo300e,

It is a pity that you even could not move the shutter with the screwdriver. May be it could be worth opening the device to understand for the fun of increasing the knowledge.

There is a spring that brings back the shutter at "zero position" when no power is on. The shutter is turning around the longitudinal axis.

I believe that the screw is acting as a stop at the end of the displacement and that is what I would like to know.

Pictures would help

Enough said, why would you offer any repair advise, furthermore, why would anybody listen?

Because, in the course of trying to fix it, I went through the testing and replacement steps recommended here, and by a variety of good shops in the area. I could not fix the problem, and needed a car that could be driven under all conditions with confidence.

I think my advice to simmo300e on his problem was pretty good.

This forum has pretty much not had the sort of nasty personal attacks like the one you just made, and I for one would like to keep it that way.

Ditto, please keep the personal attacks away.
We are only trying to help each other here.

By the way, I ordered some parts today from MercedesShop, I have never heard anyone sending stuff overnight for $9. Isn't this forum great?

Keep those personal attacks away!!!
 

Yes,
definately keep those personal (RUDE!!!) attacks away, this is a forum of people trying to help people. With the exception of the experts... Steveb and the others, I would say the rest are nothing close to experts. So information, information, information is a good thing.

Sorry folks the person who put in that rude comment needs to be put into his/her place.

Sorry to disappoint but I was unable to check what the sealed screw would do. It was stuck so tightly that the brass key socket stripped when I tried to open it. Steel won out over brass, so I guess it's not meant to be adjusted after it leaves the factory :)

However, I was able to test the old Idle Control Valve, which miraculously started working once I got it on the bench. Perhaps there was a bad connection or there's a connection fault within the unit. Either way, here's my observational guesswork:

Firstly, at no voltage, the shutter valve defaults to a position of about 1/4 open, which is around 2mm. I'm presuming, based on my experience, that at this setting, you get an idle of around 500 rpm, which is enough to start the car and can produce an acceptable idle speed if the mixture is adjusted, but not enough to keep the motor running when you close the throttle, which causes the stalling effect under deceleration.

Note that the default mode is the rest position of the shutter, and I reckon the adjustment screw sets this position. I tried to move the shutter which a screwdriver while at this position but could not. I incorrectly assumed this meant the shutter was stuck but in actual fact, I was trying to push against the stop. In the diagrams that follow, the screw is on the top and logically prevents the shutter from opening any further than the rest position. When powered up, the shutter opens downwards, in the other direction which closes the default gap and opens from the other side of the airway.

FWIW, I cleaned a considerable amount of black gunk out a few weeks ago and was rewarded with a shiny, albeit worn, shutter. However, when I looked at the shutter under power, I could see that the 1/4 section which remains hidden in rest position was still black as anything. Perhaps using cleaner while powering up the valve would be more effective.

I've attached five images showing the position of the shutter at voltages of 0, 4.5, 6, 7.5 and 10. These were applied from a transformer and read while the leads were connected to the ICV. When I took readings directly from the transformer, these translated as follows: 4.5 read from the ICV connections = 7.5v when read directly from the transformer; 6v read as 9v; 7.5v as 11v and 10v as 15.6v.

This I presumed was due to the resistance of the ICV, perhaps due to bad internal connections. My physics is a little shaky at this point as its been years since I've had to think about it, perhaps someone more knowledgable can shed light on this. If the ICV responds to exact voltage settings, and is sapping the power along the way, perhaps explains why the unit doesn't work as well as a good one. I could, of course, go get the new unit off the car and test it but I don't think so, not just yet while its working fine.

Anyway, hope this info is helpful and also hope that someone can verify my guesswork as to what's going on. I'd like to think I was right in replacing the unit and didn't get caught out by a bad connection. Certainly solved my problems, so whichever way I got there was good enough for me.

While I've got the floor, I would also like to say that this forum is easily the best of all the sources of Benz info out there in cyberspace. Apart from all the rough idle info, it was here I found out I needed to replace two capacitors to get my clock working again - what a blast that was. Thought I'd need to lay out for a new unit and ended up spending 1,000 rupiah, which these days, I'm afraid to say, is just 9.5 cents in real money.

Good work fellas!

position at 7v

position at 6v

position at 4.5 v

position at default, 0v

Simmo300e

Thanks you for the exloration you made.

I am sorry that you could not move that screw to see its function.

If I understand correctly, when at idle or at engine OFF, the shutter is in the default position.

Unfortunately I do not have a non working ICV to open it and see what the inside looks like.
I know from some drawings I have seen there are 2 bearings and one spring that could fail (+ other electrical devices indeed) and I suspect them to fail with ageeing.

Would you have the interest to open the ICV I would be interrested to have some pictures and try to imagine if the ICV would be reparaible.
I am convinced that it is interesting to know how these smart and expensive device work to unsderstand how to repair.

I think if you reread my earlier posts you'd understand that the rest position with engine off is different to the default positon when the engine is idling. It's that difference that seems to cause the stalling.

As for taking the unit apart, it looked pretty much sealed to me so I binned it. Sorry.

My car has the idle control valve that works by heat soak from the cylinder head and I've got one of the electronic ones that I want to fit. Everything seems straightforward to plumb it in but the new one has three electrical pins and my old one only has two. So- can anyone tell me what the extra pin is for or how I could wire this up?
Thanks