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Unstable Idle On My 1985 190e

4K views 26 replies 3 participants last post by  Sir_Snow 
#1 ·


Hello all, I am new here and I am seeking some help with a problem that neither I, or the people around me can't figure out. The idle on my car is rough, and the needle will stay between 500-1000, but will rev up and down at varying times and speeds. At times it sounds like it will choke out, but it never does. Occasionally upon a cold start it will die out the first time, but that may be from not cranking it long enough. I have checked my vacuum lines, and they seem good, like they had been replaced within the last few thousand miles at least. Being that the car is old, it does burn oil, about a 2 quarts a month, one every two weeks. Upon topping off the oil, the car does actually idle better, much more stable, and not as jumpy. Does anyone have a clue as to what this would be? Any help is appreciated.
 
#5 ·
I assume you pushed the pedal once on each occasion. Yes I see a bit of idle roaming but not excessive in my opinion.
It would have helped if you had captured the engine coolant temp on the videos.

You might also want to put a multimeter and either measure voltage or duty cycle on test points 3 to 2 in the circular diagnostic connector by the ignition control on the driver side. See if you can capture the instrument cluster and the multimeter at the same time.

At this point my opinion is it could be your ICV or the control of the ICV (both at hot and cold)

Please post another view with the temp included. And cold should be stone cold, not cool after a 2 HR wait. Best to be done after overnight.

- Sinan
 
#6 ·
You need to check all vacuum pipes you can find , the economy needle is in the centre at one point this shows a vacuum leak .Also fuses in the fuse box need a clean along with all the earth points to the body . Then i would check fuel pressures in the fuel distributor..
 
#7 ·
I would have captured it, but it doesn't ever show high temp or anything weird. From what I have seen it shows totally normal readings. You say that it's not excessive wandering, but when it does this, if I am at a total stop and get into drive from park, then cut my wheel hard either right or left, the car will die almost every time. I have only the need to check one more of my vacuum lines, because it's in a rather odd place. Then I will check my ICV. Thanks for the help guys. Also, I'll use a multimeter too.

P.S.
When the car has been sitting for a long time the idle upon start is usually nearly perfect. Once I give it gas is when it starts stumbling, but almost never effects it from a really cold start. It also will idle better once I top off the oil, which is odd. Hope this helps.
 
#8 ·
Yep, I missed the vacuum meter because sunlight was shining on it and it was partially showing. Trevor is right , absolutely, that vacuum has to be fixed first.

For the vacuum please keep it in idle, and push some of the vacuum operated heater control switches to see if there is an effect at all.
Also independently turn the temp control wheel from hot to cold to see an effect.
The meter should not budge when you do these. This will vindicate your vacuum meter side of things.

If the meter is not affected and is still sitting around the middle like you have it and not pegged all the way you need to start questioning the meter or some serious leak under the hood.

My coolant temperature question was not so see how hot your engine gets, it was to see how cold it really was for the cold video.
I wanted to see how things look with the open loop emissions versus closed loop. And for that, I need to see the engine temp.

Also, if turning your wheel induces the stall, you should show that in the video, skip the part about throttling, that looks normal.

Maybe I'll take a video myself of what I was looking for and post it. This will also show you what a "normal" engine looks like.
This will have to wait till tonight though.
 
#9 ·
Sorry this took a while but here is my car's idle. Vacuum is pegged all the way at all times. The clicking sound is when I was switching in different heater flap controls. Also turning the wheel has almost no effect on vacuum or idle speed. My idle is not perfect and it does roam at times but it appears to be a lot less than yours. I would say this behavior is more normal. The duty cycle (well 100%-duty cycle) is shown in the background. It seems to be more like 40% instead of close to 50% at idle. Hope this helps.

 
#10 ·
Wow, yeah that idle is a lot different than mine! My economy peg is all over the place when I am at idle usually, it changes along with the throttle of the idle speed. I should be able to really look at my car today, so i should be able to let you guys see what's happening. I got some new video, should be able to upload it soon! Thanks for helping out guys!
 
#13 ·
By the way, my car also burns oil, about the same as yours, 1 quart every 500 miles (2 fill-ups). I will be fixing that this summer. I do not believe that is your problem unless that completely messed up your O2 sensor. My O2 was replaced about a year ago.

I would keep working on your vacuum first. I bought a mityvac on line for I think $30 or so. It is a very helpful tool in diagnosing vacuum problems, flushing break fluid, etc, etc. We can also diagnose if your vacuum meter is busted with the mityvac.

BTW, my car is not at 119K, the cluster was replaced with another one and I did not re-set the odometer. My car is at ~185K miles.
 
#16 ·
Update!

I have finally had time to get under my hood and really look for the issue. I took off the air filter housing from the top of the engine, and I saw that there were two connections that werent hooked up to a hose on the bottom of the housing. After I took the hose and hooked it up, I went and turned the car on, and not only did it start better, it idled better and never choked out when I cut the wheel, no matter how far I did. However, It still does jump around a bit on the idle, but from what I am seeing from the forum, that should be fine. So, does anyone know what exactly this hose does? It connects from the side of the valve cover to what seems like the vacuum pump.
 
#17 ·
I have finally had time to get under my hood and really look for the issue. I took off the air filter housing from the top of the engine, and I saw that there were two connections that werent hooked up to a hose on the bottom of the housing. After I took the hose and hooked it up, I went and turned the car on, and not only did it start better, it idled better and never choked out when I cut the wheel, no matter how far I did. However, It still does jump around a bit on the idle, but from what I am seeing from the forum, that should be fine. So, does anyone know what exactly this hose does? It connects from the side of the valve cover to what seems like the vacuum pump.
Good progress. You did not say if the vacuum meter is pegged all the way to the stop now.....

Is it? If not you should still work on that.

Also a picture of your question item may help.
 
#18 ·
It's not all the way pegged, but it's definitely closer. I think that the hose isn't supposed to be connected to the bottom of the air filter, I am actually pretty sure that it is the ICV breather hose. I am going to see what I can do about it here in a minute.
 
#20 ·
Because you have a 2.3, your valve cover breather hose connection is different than my 2.6. SO I can not speak to that.
However your vacuum is not related to the breather hose. Make sure your Idle Control Valve hoses are not cracked up and leaky at the connection points. If they are originals they will be.

Cheers!
 
#22 ·
BTW, I've been told not to block the breather hoses. It can really mess up your engine. I can see that those connections are correct. Usually one goes to the airfilter housing end of things and the other ends up at the intake to vent the blow-by gasses.

If I were you I would inspect leaks around your idle control valve that can affect your idle as well as your vacuum as a priority.

BTW, you have proven that your HVAC has no leaks, so you are good there.
 
#23 ·
Somewhat Of A New Find

Hey Dolucasi I only blocked it like once, and not for a very long time, I was just mainly checking for air suction, thank you for the info about it though! I did some checking around for leaks this morning, and nothing seems to be out of order. The only things I have found were minor and I have already fixed them. They show no effect on my economy meter though...
Recently I found that the defrost option has the biggest effect on my economy meter, it pushes it much further towards the left side. Also, any effect that putting that hose back on correctly has apparently gone away, back to starting slow and vacuum meter is back to the hard middle.

Anyway, I was looking around on the forum for anything related to idle issues, and after that I decided to check my IACV and my air flow potentiometer. When the car was running I unplugged both of these things, and it had literally no effect on my idle, or anything for that matter. I figure it would be odd for both of them to be bad, so maybe it is an electrical issue?

Cheers, and thanks for helping me with this dumb issue...
 
#24 ·
The defrost button makes my meter needle move to the right (not left) indicating less vacuum. It is the only one that does this and it may be normal (not sure).

In my humble opinion trying to fix idle problems with a weak vacuum maybe futile. But at this point we are not sure if your vacuum meter is operating properly either. So I would still highly recommend you invest $30 in mityvac MV8000 hand pump. You will not regret it.

Have checked the hardened (most likely) large rubber hoses around ICV? Sometimes the cracks on those near the connection points do not show.
 
#25 ·
I will look into that for sure, seems worth it. Yeah, I checked out those, a lot of stuff I read pointed towards checking that out, and so I did. They seem to be good, nothing I saw or tested on them was bad. I really just want to get some idea of what could be wrong because I don't want the staling to become a bigger issue than it is right now. I have looked all over everywhere and nothing I've seen would lead to an obvious conclusion.
 
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