could faulty/dirty idle control valve (IVC) cause all these problems on w124? - PeachParts Mercedes-Benz Forum

wawago · #1 05-16-2007, 09:26 AM

Hi, I have a 88 300ce with 175000 miles on it. I have searched various MB forums and found many things can cause the problems that I am having. The problems that I am having are:

1) when I first start up the car it runs little rough - shakes a little. the rpm stays around 750 but fluctuates a little +/- 30.
2) the car runs smoothly until when it is coming to a stop or at a stop. It then will start to rattle with fluctuation on the rpm 550-800. Sometimes it stalls when reaches below 500 rpm. The car usually starts right up but sometimes it takes several tries.
3) after 20-30 minutes of running the rattle and rpm fluctuation decrease and no stall at all.
4) lastly, when the car is parked the rpm usually stays at 1000 steady until I gas it a little. Then the rpm drops back to a steady 700 or so.

I know that there are many things in the car that can cause the problems. But I would like to know would a faulty/dirty ICV cause all these problems, then decreases in severity after 20-30 minutes of driving?

Thanks

Rick

david s poole · #2 05-16-2007, 10:13 AM

you need a rebuilt fuel distributor,with those units it is not a matter of if they go bad but when.call me if you like and i can explain further.

zcc · #3 05-16-2007, 10:28 AM

Try first adjusting air/fuel mixture.

david s poole · #4 05-16-2007, 10:42 AM

adjusting it wont get the job done visit specialtauto.com they have an excellent product for a fraction of dealer cost and a better guarantee.

wawago · #5 05-16-2007, 06:25 PM

thanks for the replies.

So is it sure that the fuel distributor is the cause not the IVC?

If the fuel distributor is the cause would cleaning it help? If so is it easy?

Thanks

Rick

just-n-time · #6 05-16-2007, 07:18 PM

Rick, Dave, gave you the info, now if you try cleaning how long be fore more debrie clogs things up again? you may have a belows that is leaking and I am sure Dave has seen this problem in your type of car more than once. try it if you wish but cleaning will not repair a bad belows.

wawago · #7 05-17-2007, 03:06 AM

One more question before I get an $$$$$ fuel distributor .. a rebuilt one actually. With the problems described above which one would be the most and least likely the cause?
fuel distributor, distributor cap/rotor and ICV.

thanks

Rick

david s poole · #8 05-17-2007, 09:52 AM

the fuel distributor.449.00 with 18 mth guarantee is small price to pay for the incredible diff it will make to the running of the engine as well as a very noticable increase in mpg.it was only because i found these rebuilts that i could afford to do the swap to my own car.all of a sudden all the little things[small vac leaks,slow start when warmed up and sitting,not wanting to run a/c because of slow acceleration from standing start] dont have any meaning anymore.my car now cranks immediately all the time and i'm seeing much better mpg.if your car has 120k-150k on the engine you will be amazed at the diff.

lee polowczuk · #9 05-17-2007, 10:27 AM

I'll buy into the replacement need...but i noticed that you have to turn in your core..so they can rebuild.

Could a DIYer rebuild? I have three of these cars, so odds are i will be doing this repair at some point.

david s poole · #10 05-17-2007, 11:08 AM

bosch would never sell the parts,these people tooled up and had their own parts made plus they have the machine for calibration[which is the big deal] when you do the first car you will accelerate the program and do the other two as quick as you can.

wawago · #11 05-17-2007, 11:53 PM

Hi David,
Thank you very much for helping me so much. I am ready to purchase the reman. fuel distributor. Could you tell me how a faulty fuel distributor could cause all the problems described above? So other people with the similar problem which I know there is alot can have some understanding. Thank you.

RIck

david s poole · #12 05-18-2007, 10:30 AM

as you accumulate miles and the fuel goes thru the system the tiny contaminants that the fuel filter did not catch start to lodge in the fuel distributor and mess up the calibration.this happens very slowly and is not noticed by driver.there is no way to tell when you are driving down the road at say 2500rpms how many cylinders are lean or rich or correct.i noticed this while having a car on the emmissions dyno on the manual readout with car under load at 25mph.when i dialed in the fuel at 25 and then let car back to idle it was way too rich showing that the fuel distributor was no longer linear.even here we are looking only at results of combustion and not at the individual quantities of fuel going into each cylinder.but at least it gives a clue and logic works from there.

sublettd · #13 05-18-2007, 09:29 PM

David,

Am I understanding correctly that once the rebuilt distributor is received that it's just a bolt on and drive sequence without any further adjustment? I rcv'd a fuel filter and accumulator today that I will install tomorrow. If that doesn't fix the problems I'm having I will probably go this route. Thanks.

david s poole · #14 05-19-2007, 10:31 AM

you will just bolt on BUT you will have to adjust the mixture with the 3mm at the tower just in front of the distributor that you just bolted on.if you need more precise advise when you do it feel free to call me.

sublettd · #15 05-19-2007, 02:47 PM

David,

Understand regarding the adjustment--L=Lean & R=Rich.

Question on another peripheral issue--for you or anyone w/insight.

Sometime back I had a problem with oscillating idle and swapped the Idle Speed Contro Unit and Idle Speed Control (Slide) Valve. After the swap, the idle went up to 750rpm, whereas it had been at 500rpm. After the swap it would also rev up from 750 to about 1200 when going into park and then settle back at 750.

Did some checking this morning and discovered I have been running a US vs Euro Idle Speed Control Unit on it. Swapped the US for a Euro I'd bought off eBay. I went back to the previous Idle Speed (slide) Valve, which my mechanic had called a "universal" one. (Cleaned it with carbr cleaner before installing.)

FYI, two or three years ago I had to replace the ISCU and the slide valve at the same time when the car would die when stopped. At that time, my mechanic installed what he called a "universal" slide valve. The difference btwn the standard valve and the 'universal' is the universal has a set/adjustment screw on the top.

I now have the Euro ISCU and this 'universal' slide valve on it and the car is idling at 500rpm. You would think I would be pleased and I am, but occasionally the idle will drop down to about 300rpm. Car doesn't falter, so I suppose it's not a problem. However, it seems there is still a glitch of some sort.

In adjusting this slide valve set screw, I presume Left is also lean and Right is rich. I'm thinking that increasing the air flow (right) thru the valve might be in order. If so, would I also make a corresponding adjustment on the 3mm tower screw on the CIS unit?

I would put this to the mechanic who installed it, but he has left the area. Wish he was still here, because the guy raced Mercedes and knew them inside out.

Thanks,

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