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190E stalling issues

11K views 22 replies 9 participants last post by  1902evo 
#1 ·
Hi,

I have some annoying issues with my 5-speed manual 2.3 97kw 190E. At first, it's driving perfectly fine, pulling like it should all thru the revs etc. BUT, sometimes the engine going to stall after i take out the gear. It is happening only when decreasing speed, and seems like on speeds under 40-50km/h, not every time, but when it does, the rpm-s dropping too low right after pressing the clutch pedal/taking the gear out, and engine stalls. Never noticed it on higher speeds or increasing speed, and it seems that the rpm drop is normal that time also, they are only going too low when the speeds are under 50km/h on decreasing, but even then the engine stalling is not happening every time, over half of that time it can raise the rev-s back to normal right away. Tested it on braking, that maybe it is related when i add some brake pressure also in that time, but seems that it won't affect it directly. Now when i'm driving with the car, i try to hold my foot on the gas pedal at the same time when changing down the gear/decreasing speed when it's possible, like that it never does it, as the rev-s can't drop that much. Long story short, it seems that it is happening because of the rpm-s dropping too low after taking the gear out when decreasing speed in town speeds, but why it is happening?
Other thing to notice is the engine startup when hot, it is somewhat hard and not going to idle fine right after startup, it takes some seconds and sputtering for the engine to idle normally, when adding some gas right after the startup, it is going to idle normally much faster tho. BUT when the engine is cold, it is bang-on and starts up right after touching the key, and idle is also perfect right after it is started. I don't know if those two issues are combined or not, that's why i mentioned both of them.
About the maintenance, spark plugs, fuel filter, air filter, oil, battery etc. are all new, and i say it over, car is driving PERFECTLY well other than described above.

Anybody have some clues or is there some common issues to look out for?
 
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#2 ·
One thing to try is "carefully" spraying "carb" cleaner around vacuum lines, and under the intake manifold to see if it stumbles or increases the idle. First...carb cleaner can mess up paint, and be dangerous to spray around. Also, if the carb cleaner gets sucked into the air cleaner intake...you will get a "false" positive. But if you spray it on something and it reacts, it could be your issue. Just be careful spraying the stuff. If you find a vacuum line bad...fix it, don't block it off.
 
#3 ·
S4BIT, I have the same exact issue you have. Same symptoms, but seems a lot less severe for me. Mine is also a 5 speed, but 2.6L - 6cyl.

(1) Cold start, it starts in a fraction of a second, faster than my almost new car really.
(2) Hot start if the car has been sitting for less than 15 minutes, again not a problem. Engine temp is generally >75c.
(3) If it sits for between ~15min to 3 hours or so it takes 2 strikes. It starts right away but immediately stalls. Second key stroke it immediately starts just like a cold start. Also if I give it a bit of gas when I try to start the first time it does not stall.
(4) When I'm coming to a stop and depress the clutch around 1500-2000 RPM, very rarely the engine will stall because it seems like before it can get into the idle, there is a dip in RPM's and the engine can not recover. I believe whatever is causing this is also potentially causing the hot start issue. For me, it seems like everything just has to be right (wrong) for it to stall.

The stalling when the clutch is depressed is very rarely form me. Maybe once every 3 days. But I would like to find the root cause.
I am afraid it may get worse over time, these things always do.

It feels to me like it is an electrical issue. Perhaps even the ICV acting up. I have no vacuum issues whatsoever. Actually no issues at all, car idles pretty OK for a 28 year old car, accelerates just fine.

Sure would like too find out what the source of this nuisance is. Hopefully, someone has fixed this exact same problem before and can help us.
Seems automatics does not experience the clutch stalling as the engine RPM's never gets slammed down that fast ever.

I suppose the warm start and the clutch stall root cause could be the same (especially since we both have the same symptoms)
 
#4 ·
Thanks for the answers so far, and it's nice to hear (not that I'm lucky about your car issue) that I'm not the only one with this kind of problems.
As we have basically 2 different engines sharing the same symptoms, it SHOULD be easier to figure it out?!
 
#6 ·
A4Bit, I got inspired by your post so I decided to start debugging this issue.

I have an extra ICV so I figured I will start by swapping them out to see if there is an effect.
Before that I at least measured the resistance of each valve and they are both around 8.5ohms so no issue there.
I also measured the voltage on the ICV terminals with it plugged in and a see an AC signal of about 50% duty cycle and the an RMS AC voltage of about 7 volts and the average DC voltage is about 6 volts during idle. I think all this looks normal.

But before I could swap them out the car did one of its in a while idle hunt. Which is the idle drops significantly and the engine barely recovers. I believe this is what happens when the clutch is pressed and it coincides with this hunt and the engine can not recover and dies.

During this the electrical voltages at the ICV was not changing much at all. So I do not believe it is the ICV.

Instead what is happening is this: what triggers this action is that the airflow plate suddenly drops as if it is sucked in by some vacuum coming from below it. So the car behaves exactly the same as if one just presses down on the airflow meter and the engine is starved.

So now we have to chase down what is causing this sudden suction in the air flow meter. I can even hear the suction right before the plate moves.

I no longer believe this is an electrical problem or anything related to the ICV.
 
#7 ·
I can't remember if these cars have vacuum assisted clutches or not, but if your clutch master is vacuum assisted, the assist could be failing and causing the master cylinder to draw more vacuum, which will reduce your manifold pressure, thus sucking the plate down. If the clutch has a vacuum assist, I would start there.
 
#8 ·
Good theory A.Cabral however reviewing the Haynes manual there does not appear to be a vacuum connection/assist on the clutch master cylinder. Actually, I was surprised to find out that the master cylinder is in the car right by the clutch pedal.

It is something else. It feel like after some vacuum build-up there is a sudden release of that vacuum when it reaches a certain level. My assumption at the time is the stumble is not related to the clutch action. It is just that the idle response time is really strained with the sudden drop of engine load (due to the clutch).

Still looking....
 
#9 ·
My next guess would be brake booster then since it seems to be happening as you come to a stop, but I'm grasping at straws. Maybe clean your Idle Control Valve and air metering plate and see if that fixes anything. This issue really has me stumped though, and my car isn't the one facing the problem lol.
 
#10 ·
I'm pretty sure the stall issue with the clutch is just a secondary symptom.
It really happens once every hundred times I'm coming to a stop it seems. I'm pretty sure it is coinciding with the other idle "stumble" issue.
I'm pretty sure if we solve the idle stumble the clutch problem will go away. It is that infrequent.

I noticed that the stumble can happen any time but I notice it mostly happens when the idle control is switching from open loop to closed loop control. Appears to happen right about when the engine coolant temp is nearing 80c during warm-up.

So it seems the switch over is not as smooth as should be.

It can happen other times too, but very very infrequently.

I'll have to keep testing this to find out what else happens during this stumble. Right before it, I hear a suction sound, then the AFM moves down maybe a quarter of an inch and then the engine stalls right away. Sometimes it does recover though.
 
#11 ·
At first, thank you dolucasi for your commitment into this issue, and also thanks to other replies so far. For the issue, i don't think that it is related with the clutch, pressing the pedal just lowers the revs and then it happens, issue is more like that the revs wont be able to stay on the right idle point and drops too much under that, causing the stall. I hope i have some time soon to mess with that problem, starting to search vacuum leaks and go from there.
 
#12 ·
S4Bit, not sure if you made any progress, but I spent some time on this today.

Took the car on the road and tried to make it stall by depressing the clutch maybe 30 times, and no luck , I could not stall it.
Usually the RPM's drop to ~1000 and then eases to the normal 700. If the clutch is depressed at ~1400 RPM rarely it goes straight down to below 700 but never stalls before it recovers.

So I still think this is an issue of "stumble" coinciding with the fast RPM drop during the cluch action.

I idled the card for 20 minutes and it never stumbled either.

Since I had the air filter housing off I decided to change the ICV with the one I pulled from a 118K mile, newer car to see of there is any effect.
Sure enough by luck of the draw, the car stumbled with the new ICV as well. So the stumble has nothing to do with the ICV. Again right before the stumble the RPM's go slightly up (to maybe 1000) than there is a suction sound (like a vaccuum release), then the MAS plate drops a little and the engine stalls.

Anyway, for kicks I'll drive the car with the replaced ICV for a while to see if the stall happens during coming to a stop but I'm pretty sure it will.
This would vindicate the ICV.

More on this later.
 
#14 ·
Damn. I had one stall during the third day. So it is not the ICV. One stall in 3 days continues. That's about 1 stall in about 100 miles of city driving with a manual transmission coming to a stop.

My idle has the occasional "stumble" still. if it is bad enough it can even stall just idling. No idea what triggers it, seems to happen once or twice a day. First the RPM's surges to a little over 1000 than it stalls. I believe it is when this is coupled with coming to a stop is when the car stalls.

Still looking and any advice is welcome.
 
#15 ·
Let's say your fuel pump, fuel filter, fuel pressure regulator, and injectors are confirmed to be in good operating condition but car still stalls, bogged down when gas pedal is pressed, or erratic idle, I'd say the problem is the rubber diaphragm in your fuel distributor. It's either dirty, worn out or too flimsy, or may have a hair-pin puncture making it unable to control or manage gas pressure to the injectors.

Our cars are old and these rubber diaphragm can not maintain their function forever so they will eventually have to be replaced.

I've done the FD overhaul myself and the result is way better than I expected. The issues described above are all but long gone memory.

I would caution anyone who want to do the FD distributor overhaul to study and review the thing in length before attacking it... you need to have a backup plan. The FD overhaul will definitely test your DIYer limits and patience... it should only be your last resort.

Here's my write-up, sorry, it's not very detailed but I share what I can:

http://www.benzworld.org/forums/w201-190-class/2440569-fuel-distributor-fd-overhaul.html
 
#16 ·
Thanks Javelin, thats a very good write-up and I'm sure I will need it in the future.
Fuel filter <20K miles
FD <30K miles (was either overhauled or a rebuilt one put in by the PO)

When there is fuel delivery problems the symptoms are generally different.
My car has no issues accelerating, during start-up, or generally idling.
Actually most of the time it runs like a brand new car.

I have a hunch this is more vacuum related and of course it could be vaccum in the fuel distributor that is the problem and it only stumbles when the vacuum is lowest (idle). And that only happens once a day and sometimes less frequent than that. Is the diaphram you mention actuated by the vacuum in the intake?

At this point, while I'm still diagnosing, it is too early to start work on the FD. Eventually though if/when it gets worse I will have to.
 
#17 ·
S4Bit, how are you doing with your stall while you are coming to a stop?

It has been 10 days and I have not had a stall myself. All I did was to fix a couple of minor vacuum leaks in some small rubber connectors. One had a crack in it and the other was loose fitting. Now the vacuum is even stronger and it idles better too. Long story short, after this the engine does not stall.

Sometimes when the engine hits 80c during warm up and lambda control switches from open loop to closed loop it stumbles but even that does not happen very often anymore, maybe once a week. And it never stalls.

I'll give an update in another week. Keeping the fingers crossed.

BTW, the Mityvac hand tool is very helpful for finding vacuum leaks, well worth the $50.
 
#18 ·
I think we may have lost S4BIT who is the original poster on this, however for the sake of future readers, I do have an updates.
After months of diagnosis effort and help from the W124 forum, I believe I have gotten to the bottom of this issue.

Simply put 3 letters, OVP. Replace it with a new KAE unit (do not use old junk yard parts) and this problem will go away and your car will idle better too.

My guess is that somehow the OVP starts to misbehave intermittently once it is maybe 10 years old. So it is a wear item.

Case closed.....
 
#20 ·
Hello there. I know no answer has been posted since 2017, but i would like to add to this discussion. I have a 1992 190 1.8 automatic, in Greece. I bought it from a friend who restored the car 4 years ago but seldom drove it as he lives abroad. Long story short, the car drives perfectly, but when I slow down to a stop sign or make a left or right turn it suddenly stalls. I put is in neutral, turn the key and starts again. Ususally it does not do it again during a drive. Never stalls when driving at 40-50 mph, etc, only when it slows down.

Based on this discussion I changed the OVP and the Fuel pump relay (all new) plus the fuel box, but it still does it. I will visit an old/exprienced mercedes mechanic in 2 days and will let you know about the progress soon. Thank you
 
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