could faulty/dirty idle control valve (IVC) cause all these problems on w124? - Benzworld.org

wawago · 05-16-2007, 07:18 PM

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

Arnie2 · 05-17-2007, 04:53 AM

Yes, it does seem like it could be the idle-control valve, (or you may have an intermittent leak in a manifold gasket.)

If you turn the ignition key to position-II (do not crank the engine) and wait about 30 secs, you should hear a click-clack which is the system testing the idle-valve, by fully opening and closing it. You can check that it's doing this.

As you say, there are many systems on these engines that could cause problems and the built-in diagnostics are very limited. My guess in this case (particularly because of your point No.4) would be the idle-control valve.

[BTW: The +/-30 rpm variation you mentioned in point No.1 could be caused by the a/c compressor switching in and out, so best to have a/c off for any testing.]

Inline6 · 05-17-2007, 11:44 AM

The Idle Control Valve (ICV) is an easy DIY. Since it controls your idling, you can start from there. All you need is a can of carb & choke cleaner. If you have a multitester check the resistance of the wires connected to it, reading should be betweeen 10-20 ohms. And since you will be removing the air cleaner assembly, you might as well clean the airflow sensor. Cleaning these two items certainly improve your idling & start-ups. Good luck.

wawago · 05-18-2007, 06:24 PM

thanks for the replies
I have cleaned the ICV and airflow sensor. The problems still the same and persist. I am kind of leaning toward defective fuel distributor.

Thanks

Rick

Inline6 · 05-18-2007, 10:02 PM

ICV & AF sensor clean-up didn't help at all? How dirty were they?
Could be your fuel pressure regulator too, or you can check the individual pipes of the fuel distributor if you want. Check the fuel distributor filter also, it's located on its side, screwed-in to the FD.

Yacht Master · 05-18-2007, 10:15 PM

Quote:

Originally Posted by wawago

thanks for the replies
I have cleaned the ICV and airflow sensor. The problems still the same and persist. I am kind of leaning toward defective fuel distributor.

Thanks

Rick

Make sure you have clean fuel
check for a vacuum leak
check again for vacuum leak
repair the vacuum leak

wawago · 05-19-2007, 08:57 AM

They were not that dirty. As for cleaning the FD and each tube I think I'll leave it to the pro.

I always use brand name gas mainly Cheveron and Mobile.

Double checked for vaccum leak... I didn't notice any difference in RPM. Before this vaccum leak test my RPM at idle has been fluctuating +/- 30 without AC on.

Saving now for a rebuild fuel distributor but will take it to a reliable MB mechanic first. I hope is something simple.

Rick

wawago · 05-21-2007, 02:35 PM

update:
I took it to the famous Mr. MB Motor. The owner Enrique found out that my car was running too lean. He adjusted and now the car doesn't stall and idling a lot smoother. I'll wait for 2 more weeks to see if that really fixes it for good.

Rick

Yacht Master · 05-28-2007, 07:18 AM

Quote:

Originally Posted by wawago

update:
I took it to the famous Mr. MB Motor. The owner Enrique found out that my car was running too lean. He adjusted and now the car doesn't stall and idling a lot smoother. I'll wait for 2 more weeks to see if that really fixes it for good.

Rick

OK, like I said vacuum leak. What your mechanic did was to put a band-aid on your problem. Think about it, if you have a vacuum leak it leans out your mixture, did you ask him how the mixture went out of adjustment? Believe me you still have a vacuum leak.

wawago · 07-18-2007, 04:07 PM

Update: after two months

Actually, he did check for vaccum leak but couldn't find one. After he adjusted the fuel mixture the car ran better but still idled rough at stop light and stalled occassionally.
He suspected the fuel system is dirty and suggested that I put two not one 12oz bottles of Techrons in the gas tank. He warned the cleaning process would take some time.
After a tank of Techron it improved a little. After another week I cleaned the car 3more times each time w/ two 12oz bottles. Now the car idles rough at 10 if before was 90 in the scale of 100. No stall for little over a month. I didn't want to report back too soon until I gave it sometime to be sure the result was real.