SSS (sudden stalling syndrome)
 

It happened again in the same exact place. Right in front of my house while slowing to turn into the driveway. Only indication is the steering suddenly got heavy. No shuddering or weird noises. The car runs fine otherwise with just a slight random miss at idle. I do mostly city driving so there are plenty of similar conditions thruout the day. Is my mailbox sending out gamma rays?

As you know, I also have a 85' 380SE. You may also know I was having a stalling problem, but mainly when placed in gear, when the engine is fully warmed up, but there have been three occasions within 3 months when it stalled while stopping. Once was when I came to a stop to make a right turn. It started right back up and went on. The other time was when I stopped at a traffic light. When it was upshifting, the idle was going down too far and at the end, it stalled. The other time was last week when I was turning into a parking space at the supermarket. It was a sharp left turn (as I was swinging back up toward the other direction), and like you described, the steering became heavy and I noticed the engine had stalled out, but I went ahead and coasted into the space. It has not stalled out since, nor has it stalled when placed in gear, BUT over the past few days (since last Tuesday), temperatures have only been in the 50s, so the engine is running cooler, hence the decline in stalling.

I am wondering if we may not have the same problem- whatever it may be.
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1985 380SE - 265K miles! :D

Well its been doing it more lately. When it happens its during coasting with gentle braking. I've been watching the tach sometimes dip below 500 and then jump back up. I can't force it to stall out, it just does it on its own. 99% of the time, there no sign of a problem.

I found some history on this car. Turns out it had this problem for a very long time, like since it was brand new! The original owners only kept it for 2 years because MB could not figure it out. Then my dad had it and spent thousands on new parts, but the problem never was resolved.

I though I had it licked when I tightened up various connectors, and it hadn't stalled in months. Now its bordering on dangerous, since it can happen on a highway off-ramp for instance, and its unpredictable.

All vacuum hoses are tight with no cracks. I'm wondering if the little vacuum bypass upgrade on the ICV might fix this?

RAYMR.... I am still having the exact same issue with my 85' 380SE and it seems to be getting worse.

Last time I drove it (Thursday afternoon), I had taken my mother to the post office and was in the car waiting for her. I left the engine on and left it in drive, so I would not have to deal with the stalling when I placed it in drive. Strangely it stalled out just as I let my foot off of the brake. It started right back up and went on. Before that when I stopped at the bank, I had turned it off. I restarted it and placed in drive and it stalled. It did this twice, then it finally went. This was around 3pm. The engine temperature was at 100*C. Later that evening, I drove it again around 8pm and it did perfectly, as the engine temperature was cooler. I had driven another car earlier in the day. I have 4 cars, but I enjoy driving this one and drive it despite the stalling, but I am about ready to stop driving it later in the day (or on that 2nd or 3rd trip out).

Sometimes my idle will drop to almost "0", yes "0", RPMS when I place it in gear, but it does not stall, but sometimes it does stall. Also, when hot, it idles at 900 rpms, but does not keep it from stalling. Its crazy. Sometimes when I get home, I will "test" it and place it in park, then drive and I cannot make it stall. Like yours, it stalls when it wants to and gives no warnings.

I also do not know it has stalled until like you said, the steering gets heavy. Sometimes mine also stalls when I make a turn into a parking space, or on the slow turns as I near my house. It is starting to get embarrasing, because the other day, it stalled at a traffic light. I was setting there for about 45 seconds, released the brake and it stalled as quickly as turning the ignition off. It started right back and I was on my way. It seems to be getting worse.

I am thinking it is the idle control valve, but now it seems to be linked with the brake pedal. Perhaps a vacuum leak is the problem with mine, but who knows with these cars? :)

Good luck to you. Hopefully we can get these cars back in proper working order.

380
 

today at work i had 2 380 SL's (same engine as both yours cars) that had similar stalling issues. one had the fuel mixture set way too lean, enrichening the mixture fixed it. and the other one had a defective ov relay. have either of you checked these two items? the easiest way to verify if the ov relay is working is remove the air cleaner and see if with the engine running that the frequency valve is working, it will be on the drivers side near the air intake. if it is buzzing or can be felt vibrating it is working.
you can also un plug the idle valve if the ov relay is good idle speed will raise, next would be to check the fuel mixture.

Thanks Carson. I will check those items soon (on my next day off.... Wednesday).

Do a search for w124 + sudden stall.

I take it that your car starts right away, right?

That seems endemic to certain Benzes.

Check the hall effect sensor in your car. Also check the fuel pump and fuel pump relay.

This morning I turned the mixture 1/16 turn to the right. I took it for a drive and it *seems* better. Over the next few days I will know for sure. Thanks!

be sure not to turn the mixture too far, make sure the mixture control is working properly do as i said above. you can check and adjust it with a DMM set on duty cycle, black lead to ground, red lead to pin #3 on the x connecor on drivers fender well. i usually adjust them to oscillate between 38-45%.

I both unplugged the OV relay and idle valve, and idle speed increased in both cases. The duty cycle always reads higher in this car. Now its between 74 and 80%, with red lead on pin 3. It would slowly climb to 80 then pop back down to ~74 repeatedly. No stalling yet.

that seems too lean to me, ideal is under 50% now lower than 35 no higher than 50

It runs very badly if I try to get it in that range. Maybe it has ECU strangeness, or maybe its part of the original 'uncurable' problem.

have you tried another ecu? have you tested or replaced the oxygen sensor. have you tried runnung it with the ecu disconnected?

The O2 sensor is new. I haven't done anything with the ECU since my dad had it replaced several years ago. The car passed emissions a few months ago and mileage is decent, so the equipment is mostly working.

I just checked the braingears manual. For my year car there is no specific on/off ratio, but the ratio at idle should be close to what it is at 2500 rpm. I guess I'll check that next.

50% is what mercedes calls for in the manuals, i adjust to the rich side for better idle quality and to compensate for engine wear and possible vacuum leaks. seeting it where i do does not have negative impact on emissions. so try 50% and see what happens, be sure to rev the engine to get the oil hot, on the side of the engine near the oil filter housing there is an oil temp sensor that only enables lambda when the oil is good and hot.

Always check for vacuum leaks with a stall situation, especially when heavy on the brakes.
Second...and less common, is a stall situation when cruising along straight line, no turns, even gas input, just maintaining speed....and she quits. I have seen bad spark plug wires arch enough to shut down the motor, roll back the key, turn to ON position and comes alive again. It took me a year on my sisters audi 4000 to figure this out. Dealer could not find, indy mech could not find. Could never reproduce in a shop. FYI..wires were only 1 year old, and broke down real quick for some reason.
Moral is.... every once in a while, open your hood at night...pitch black, and see if you are getting a light show.

The mixture tweak seems to have helped, though its too early to know if its 100% cured. I'm curious about the duty cycle discrepancy. But since the car runs fine, I'm not feeling compelled to locate and swap out ECUs, etc. Plus I'm a little afraid of what I might find, and/or breaking something else in the process.

The ratio at 2500 rpm hovers around 70%. Idle is now 70-76.

I'd like to find out if any other 1985 380s (86560SEL?) want to be at 70% duty cycle instead of <50%. Or do I own a total odd-ball?

as i originally said the two i worked on last week at work were set around 35-40% when i checked ignition timing one was at tdc and the other was at 11 before. both ran fine so i left them as is. timing can also affect the ratio %. you may check and see what it is at, should be with vacuum disconnected and plugged

Stalling
 

I had the identical stalling problem with my '88 260e. The culprit turned out to be the airflow sensor pot. It is a variable resistor on the front of the airflow sensor that senses throttle positon. The carbon on the circuit board wears out first in the idle range (where it rubs most of the time). A slight blip (loss of signal) is enough to kill the engine with no warning at all.

You may be told that the entire airflow sensor needs to be replaced but I bought the sensor pot at Olyparts.com and changed it myself. Hasn't stalled since.

I don't know about the timing yet, but I do know I have it slightly advanced to use midgrade fuel instead of regular. The power seems a little better that way.

About the duty cycle, heres what happens:

The car runs best at around 70-73%. If I turn the mixture adjustment to the right (rich) the reading goes up. It eventually maxes out at 90%, which I assume is the limit where lambda stops working. If I turn it left (lean) again and go towards 60%, it really starts chugging and sputtering. So what does this mean?

did you say if you had looked for vacuum leaks?

I inspected, and replaced anything that was cracked or leaking. Including the tube that goes to the transmission.

With the mixture adjustment, although better, the engine would still almost stall sometimes. I decided to pull the ICV and clean it out per the advice found elsewhere in this forum. A lot of black gunk came out so I wouldn't doubt things were getting sticky inside. Reinstalled, and its way better now.

Just a follow-up. Cleaning the ICV has *completely* solved my stalling problem. I'm not positive, but it looks like it meters crankcase gasses into the intake, and not fresh air. That would explain the buildup of gunk inside. I would make ICV cleaning part of regular maintenance.

To update, my 85' 380SE is still stalling when hot/warm, but it has not gotten worse, but it is getting old.

I phoned one of the local Mercedes repair shops and he said it could be the idle control valve, or the computer, or a vacuum line leak. Upon recommendation, I disconnected the idle control valve with the engine running and the idle did go up to 2000 like he said it should. Does this mean that the idle control valve is OK? Seems like the stalling is worse when going into reverse and it harshly engages into reverse, especially when the engine is hot. I am assuming this harshness is a different problem.... ??

He said to use brake cleaner and spray around to check for vacuum line leaks? This seems dangerous, since this is extremely flammable? Or am I being to paranoid? He also said I could remove the valve and spray WD-40 in it, but I am assuming this is if there was no change on the idle when I removed the connection from the valve? There was the RPM increase.

I do not know what else to do. I had about decided to get a brand new car, but after looking at them, seeing the prices and the low quality that seems to plague many of the cars these days, I think I may be better off keeping my 85' 380 for awhile longer (at least until the timing chain/rails break- then part it out, because with lifter chatter on the passenger side and 270K miles, I do not want to spend alot of money on it, as I have already got my monies worth out of it).

Any further advice about my stalling problem would be appreciated.