380SE running very poorly until warms up- vacuum leak?

[86560SEL]

I had posted here before about the sudden stalling my 380 sometimes does after the engine is fully warmed after I place it in gear or stop at a traffic light. I have been told it could be the idle control valve.... checked that and it is fine. Idle goes up when it is disconnected. I have not yet tried to check for vacuum leaks, as mentioned here and recommended to me by some here. I was told to start the engine and spray brake cleaner around (on cold engine) to check for leaks.

Well, to update, strangely, the engine has NOT been stalling, but when I first start it of the mornings, after about 10 seconds, it starts missing and "choking" itself and puts out "gas" (also known as carburator smoke on older carburated cars) from the exhaust. Its like it is getting too much gas. If I hold the accelerator steady when in park, it misses, but upon acceleration, or even in gear at steady acceleration, it smooths out. It will do this now until the engine almost completely warms up. It did this slightly last winter, but only if the temperature dropped below 40°. During the summer it did not do it, but it was doing the stalling. Now the stalling is gone, but it is running very poorly when the engine is cold if the temperature drops below 60°, which is has been doing for the past few mornings, since summer is winding down. I have a feeling it is only going to get worse and worse.

Does it sound like this could also be a vacuum issue causing this as well, or could something else be causing this?

Thanks in advance!

[wbain5280]

Based on what you wrote, I would look at the vacuum lines. There are many of them, the idle air bypass hoses to the injectors, the injector seals and the rubber donuts between the two manifold sections, upper and lower plenum.

How're the timing chain and guide rails?

BTW, I have a similar problem on my 420SEL which starts poorly and runs poorly, at first. I'm going to replace all the vacuum bits and pieces.

See sections 7.3 and 14.

http://mb.braingears.com/126_DISC2/program/engine_380SEL.htm

Page 4 has a good picture

http://mb.braingears.com/126_DISC2/program/Engine/107/M116_38/14-450.pdf

I'll keep you posted on my progress. I'm going to check my O2 sensor first by measuring it's output. If it's bad, I'll go for the generic 3 wire version and solder it in. Once that's done, I'll tackle the vacuum lines.

I have to get it in for a safety inspection first. It should pass with flying colors.

[86560SEL]

Thanks for the reply! I will check those lines tomorrow. Will I need to remove the air cleaner to gain access? If so, will the car run with the cleaner removed? I know some cars will not. I also forgot to mention that the car starts very easily- even first thing in the morning. It starts only after a second of cranking.

About the timing chain/rails.... did you ask that because that can be the potential problem? I hope not, because to tell you the truth, I have no idea when they were changed. The car has 267K miles on it and the guy I bought it from when it had 250K had no idea either. He had bought it from the original owners when it had 200K and he said he never asked them and he had never changed them. I only paid $1000 for the car and it is so old, I have no intentions of changing them either. If that is the cause, I will probably sell it and let someone use it as a parts car- which would be a shame, because the body is still dent and rust free and the interior is in excellent shape. Only negative is dead paint. Also, the transmission and rear end are both in perfect working order and EVERYTHING except the cruise control, auxillary fan and A/C work perfectly... all lighting, gauges and windows, heating, sunroof, etc. work fine.

Hopefully it is as simple as a broken vacuum line. If not, I guess off to the junk yard she goes....
Thanks again!

[86560SEL]

I checked those links and hopefully all of that on top of the engine does not have to be removed, or I will sell the car. I would not even know where to start... not mechanically inclined and would not want to spend alot of money on it, since it is so old. I will check for air leaks though with that brake cleaner fluid.

Thanks again!

[86560SEL]

Would worn timing chain and rails cause the miss and "choking" when cold? Surely someone here knows more about these cars. I am getting ready to junk this one. Even the local repair shops act dumb. At least one I called.

[86560SEL]

Oh.... also seems like it is getting low on power. Hopefully vac leak will also cause that.

[raymr]

Sorry to hear of the problems you are having. Its pretty much a given that something will break over time, even on a grand old MB. You either learn to fix it yourself, or you pay someone else to do it. Trouble is, the skills out there no longer match what these cars require, so aside from a standard brake job, etc., you don't know what you're gonna get. Thats why I invested in a fuel pressure tester and a few other specialty items to help me diagnose whats going on. I have my car running at 99% (stumbles a bit after a cold start, but clears up after a minute of driving).

So you need to either:
- dig in and learn all about your car and get the tools so you can DIY
- find a friend or decent indy who can help you
- sell it while you can still get something for it

[86560SEL]

Thanks. Well, it was running a little poorly last winter, but as temperatures went into the 60s and 70s for lows, it was fine. I would not have to let it warm up at all. Now that it is cooling again, not only is it doing what it was last winter, its worse- so whatever it is - is getting worse. Sometimes even after it warms up and it shifts into higher gears and the RPMS lower, it will miss for about a second, then smooths back out. Whats strange now is that my stalling problem has seemed to subside- at least for now.

I still have to check for air leaks. I have been so swamped, I have not had a chance. I will probably check it Sunday afternoon. Something has got to be done! Maybe you are right, maybe I should sell it before the timing chain snaps, rail break, or even the tensioner. Lord only knows when/if they were changed.

[gmercoleza]

Or why not just change the chain and guides? Not an impossible job, and parts would certainly run you far less than the upfront investment in another car, along with a new set of problems you might possibly inherit. I bet if you pumped $1000 into that car and devoted 2 or 3 weekends to repairing it, it would run like new and would be good for another 50,000 miles.

[86560SEL]

I would change them, but the engine has a faint knocking sound between 1600-1900 rpms. It has not gotten any worse in the 10K miles I have owned it, but I am concerned that my engine is simply worn out and really do not want to put $$$$ into the engine if it is knocking anyway. I have been told that the knock could be a worn camshaft on the passenger side of the engine.

Transmission wise, body wise and interior wise, I know this car would easily last another 100K. Body rust free, interior in excellent conditions and everything still works (save for the A/C).

[86560SEL]

Thanks - you are right- I probably should sell it. I would like to see a MB fan and a DIY'er to buy it- replace the chains, etc and find out whatever is causing the rough cold idle/hot stalling.

to update, I was told by the mechanic that replaced my PS seal that noise was probably just the lifters too- so not to worry too much.

I asked him about the poor running engine when cold. He is a Volvo tech, and he admitted that he was not that familiar with Mercedes, but he suggested that it may be some sort of sensor that was thinking that the engine was hot, when it was cold and visa-versa. He listened around for vacuum leaks and did not hear any he said.

So, here are the updated details- some things have changed.
When it is cooler outside- when I first start it in the mornings- it runs smoothly, until I press the accelerator after it is running- then it will start to "stutter" and chug alittle. Like its misfiring. There were occasions when it did that, that it was putting out a gassy smelling smell out of the exhaust. I let it run for a bit and it clears out- then I take off. Then it will miss only for a second after it shifts into the next gear, when it goes to a lower RPM- then it clears out until it shifts to the next gear- then clears out after a second. Also- I have noticed- that when in gear- it idles smoothly after the engine warms up, but when in park or neutral, it misses (shakes). I have installed new plugs, but not plug wires. Could this possibly be the culprit? They look original, but still in good appearance condition, but I know that could mean little. However, I do not think that would cause the stalling the in the summer when the engine is hot.

Another thing- about the engine temperatures. When the temps are cooler, the temp gauge rarely goes above 85°C and when on the road- it goes down to about 60°. When it is hot outside- when in town - stop and go driving, the gauge goes to about 120°C, but when I get back on the highway or freeway, it goes back down to about 90°C. I think a thermostat may be in order? Also, I KNOW for a fact that the power auxillary fan is on the fritz. It has never worked and when I install a new fuse, it instantly pops, so something obviously not right. I tried disconnecting like someone suggested to see if it still blew a fuse, but I cannot get it disconnected.

I have already bought a newer truck, but still like to use the MB as a daily driver, which I am still doing. I just chug along until it warms up. I may still sell it yet to someone that has the time, money and know how to give it the attention it needs.

I am wondering if the thermostat, or a sensor of some sort may be causing some of the problems, rather than a vacuum leak? Whether I sell it or not, I would like to get it running smoothly again.

Thanks again!

[wbrian63]

The thermostat should keep the car at about 90c minimum. If you're seeing the temp cool down to 60c while driving, likely there's no thermostat at all, or the one you have is stuck open. No thermostat will also cause the coolant to circulate too quickly, which can cause overheating - the coolant must spend the appropriate amount of time in the radiator to allow the heat it contains to be removed.

One way to check for a missing/stuck open thermostat is to start the car when it's cold. Have the hood up when you start the car to keep the underhood temps from climbing too quickly. Wait a few minutes - maybe 5 at most, and touch the upper radiator hose about mid-way between where it connects to the radiator and where it attaches to the thermostat housing. BE CAREFUL of moving parts, as this must be done while the motor is running. The hose should be at or near ambient temperature. The hose should remain relatively cool to the touch until the thermostat opens, at which point the temperature of the hose will change rather quickly. If it gets warmer very gradually, then likely the 'stat is stuck, or is missing entirely.

Since your A/C is out and the aux fan is not running, you will likely see increased temperatures in traffic in warmer weather, but I'd think that the engine fan, if the viscous clutch is working properly, should be able to keep you out of the 120c range - other's may have different ideas here, I'm still learning about my Benz. I've read several posts that talk about the "rag test". I assume this to mean that if the clutch is operating properly, when it's fully engaged (I'd guess at about 100c on the temp gauge), a rag, when placed across the shroud of the electric fans, should be held in place by the airflow. Others suggest that a fully engaged clutch will cause the fan to stop spinning almost immediately after turning the engine off.

I'd check/replace the thermostat. The work is fairly easy and the parts aren't that expensive. Modern cars MUST have a properly functioning thermostat to run properly. Just be sure to follow the instructions carefully on replacing the 'stat on your car. I missed one little line in the instructions when changing mine and had a devil of a time getting the air out of the system.

[Mike Freeman]

In your first post you said the engine smoked after starting! Is it black smoke or blue/white smoke?
Black smoke would indicate the mixture is too rich (check the vacuum lines to the warm-up regulator)
Blue/white smoke would indicate worn out valve guides (oil fouled plugs will cause an engine to run badly till they clean up.)
Mike

[86560SEL]

Thanks for the replies guys. I think the thermostat may be part of the problem.... I will replace it posthaste.

Mike- it only did the smoking a couple of times and yes, its a black smoke... it was "chugging" when it was doing this. BTW- where is the "warm-up regulators" on these cars? I have never heard of them.

I have never seen any blue smoke from this car. Despite nearly 269K miles, it does not have any oil smoke, nor does it leak or burn any oil between changes. Amazing I know.

Thanks again.

Originally Posted by Mike Freeman

In your first post you said the engine smoked after starting! Is it black smoke or blue/white smoke?
Black smoke would indicate the mixture is too rich (check the vacuum lines to the warm-up regulator)
Blue/white smoke would indicate worn out valve guides (oil fouled plugs will cause an engine to run badly till they clean up.)
Mike

[86560SEL]

To update... I was going to TRY to replace the thermostat today, but the cheapest I could find at a local parts store was $30. and I can get one here on the shop for $29.87. I was thinking $8.00 when I was thinking thermostat, then I remembered that I did not have my 95' Suburban anymore. Thats how much it cost for that one and it took me 5 minutes to replace. I have not even looked at the MB to see how difficult it will be. I guess I will have to bite the bullet and pay $30. for a thermostat.

Can anyone give me a quick description of how difficult it is to change? I am sure its not as easy as it was on my 95' Suburban with the 350.

I really think this may be part of my problem. I have been driving it to work again daily. In the morning, when I first start it, it runs fine, no matter how long, until I "move the accelerator" a bit, then it will start spluttering and missing for awhile. When I leave, its generally OK, but even after it warms up now, it will momentarily miss when it first shifts into the next gear for about 3 seconds, then it clears back out. It did this a little the first winter I had it, but stopped when spring and summer was here, but then it had that occasional stalling. Since this new thing has started and temperatures have cooled again, it has not stalled the first time, which is strange.

I am 100% now that the thermostat is bad/missing. The other evening, it had dropped to the mid 30s and on the highway, my engine temperature dropped to 55°C ! I went home and made another run into town. I had to stop back by my aunts and I did not get out- she brought grandpas meds out to me. We talked awhile and I looked down any my temperature gauge was up to about 115°C! As soon as I left, it slowly dropped back down to about 70°C on the highway. Now I am wondering- will a bad thermostat that makes it run too cool on the highway also make it run too hot when idling at a stop for an extended time? Keep in mind that auxillary fan is on the fritz.

I am still thinking there is more to the occasional misfire, other than the thermostat.... I am wondering if it may be the spark plug wires faulty? I replaced the plugs about 3500 miles ago, so they should be OK.

I may have to do some traveling for work for a couple of months starting in a couple of weeks and I would like to get this car running good again, because I do not want to drive my truck and rack up alot of miles on it.

Thanks again.