Inconsistent cold start behavior, 300E
 

I have a newly acquired 1992 300E, 77,000 miles. I am not very knowledgeable about the 300E, or gas engines in general. I had driven MB diesels for 35 years. So I was startled and confused by a stalling problem I have had with this car.
Four times in the past 2 weeks, it has stalled shortly after starting. In 3 of the 4 cases, the weather had been damp (fog or rain) for some time. In the 4th case, there had been rain the night before, but a clear cold (30s) dry afternoon. In all 4 cases, the behavior was: Successful start from cold, drive a short distance (hundreds of yards in 2 cases, about 0.7 mile in two instances), then slow in preparation to stop. Engine dies. Difficult to restart. Have to put accelerator to floor to start it. Then it runs normally, and there is no further trouble once car is warmed up.
I have also had 2 incidents of difficult initial cold starts after engine sat for hours.
By the way, I am in Massachusetts, and daytime temps have been mainly in 30s and night temps mainly in 20s or teens. We have had frequent snow storms this month, as well as the rain and fog I mentioned.
Spoke to my mechanic. His immediate reaction was to start by replacing the OVP relay. From reading many posts here and on MBCA web site, I saw that OVP relay was regarded as a frequent culprit for many types of problems, including some more or less similar to my cold start/stalling, so I agreed to do it. The old one was of a different type that mechanic said was "out of date" and should be replaced on principle, anyway. I bought one from MB dealer, he put it in. While doing so, he observed that the spark plug wires were in mediocre shape and suggested we should do a tuneup, check plugs and wires, etc. But he said, let's do that after you drive a couple of days with the new OVP relay.
The 4th stalling incident occurred the afternoon after he replaced the relay, so clearly that was not the cause, or not the only cause, of the problem.
In thinking about the stalling incidents, I have noticed one other thing: The engine does not behave consistently when started from cold. Sometimes it goes into the high rev/delayed upshift mode, very noticeably, and other times it does NOT seem to do so. On at least two of the stalling incidents, when I have had trouble re-starting the engine and have floored the accelerator to start it, it has definitely gone into the high rev/delayed upshift mode. I suspect the engine weas NOT in that mode when it started the first time and then stalled. So it seems as if the engine either does not reliably "know" when to go into that mode, OR it cannot or does not do so when it should.
Any thoughts on whether there is one problem here, or two? Is it likely that the inconsistent cold start behavior (i.e., whether or not it goes into delayed upshift mode) is related to the stalling? Any suggestions for what would cause the inconsistent behavior?
Thanks for input!

The OVP is frequently blamed for many problems and seems to be the first culprit when a problem arises. I don,t know why.
First, I'd make sure the ignition system is in top shape. Damp weather is the ennemy of tired wires. Spark plugs, distributor cap, rotor, ignition (coil) wires. This is the first step.
Then, the fuel system: Fuel filter, fuel accumulator, check valve.
A good clean-up of the fuel injectors could also be appropriate.
Good luck
jackD

Sorry I didn't see this thread earlier, because I would have ruled out the OVP...oh well you dodged a potential headache in the future, as the OVP causes "hot start" problems and rough idle issues.

Jackd is correct in telling you to look at the ignition system. Damp weather does indeed play a factor in problems in this area. I would put my money on the ignition coil(s). I don't remember when MB changed the configuration, but you either have one, or three.

300E continues to stall after 2 trips to shop
 

Several weeks have gone by, the car has been in the shop for several days, but the stalling continues.

My own mechanic replaced the plugs plug wires, distributor cap and rotor. No change in stalling behavior.
As weather warmed up, stalling became more frequent. Last 2 or 3 weeks, the car stalls nearly every time I drive it. Always starts OK, then stalls as I slow for a stop or turn in the first mile or two. Usually, I have to apply the gas pedal to get it to re-start. That is, I cannot start it the way you are supposed to, with your foot off the gas pedal.

My own mechanic referred me to an MB dealer that he claimed had a good technician team and would probably help. The MB dealer had the car for 3 days this past week. They measured the "lambda," whatever that is, and found it was "way out of spec," and adjusted it. And the mechanic found there was a pin on the connector between the voltage regulator and the alternator. They recommended replacing the voltage regulator, which I agreed to. They supposedly tested all sorts of other things, found nothing else wrong, and found no codes in the computer. It cost me $350 for their efforts. Plus the previous tune-up cost was about the same, as I recall.

The car started OK when I picked it up at the dealer, but the engine probably was not cold. Yesterday, we had snow and I left it running while I cleaned off the car, so it was so thoroughly warmed up, it might not have stalled anyway. It did not stall later in the day, in several trips at varying intervals. So I thought it was OK. I even imagined it was idling at a higher RPM and was idling smoother. Probably I was just seeing what I expected to see.

But today, when I started it first thing this morning, it stalled just as in the past! No improvement. It stalled 2 or 3 times in the first 2 or 3 miles of driving. Even stalled just as an ambulance was coming up behind me and I could not get out of the poor devil's way! Very upsetting.

This afternoon I spent a couple of hours reading the technical manual and trying to figure out the very complicated engine control systems on this machine. My interpretation is that there is a function that adjusts the idle speed during the warming-up period, when the coolant temp is below 80C. I note that the coolant temp sensor is the only signal that goes into both the idle control and into the control that delays the upshift from gear 2 to gear 3 when the engine is cold. As I noted above, I think, the car does not consistently operate in that delayed upshift mode. So I suspect the coolant temp sensor or the cable that feeds the signal to the control systems.
I tried to test the coolant temp sensor, but could not find instructions in the manual for how to do it. I could not see how the cable comes off. Does it pull straight up? Or does it unscrew? Or does it come off at all? I have a good digital ohmmeter, so I was going to measure the resistance and compare it to the specs in the manual.
There are many other devices and functions that could be wrong, from what I can see, and I do not know which of these the MB technician tested. SO I could be leaping to conclusions regarding the coolant temp sensor.

Since I have already spent about $700 trying to correct this problem, and since the mechanics obviously would have tried the obvious and common things first, I despair at the thought of paying these guys for more hours of witch-hunting. So does anyone have any input, suggestions, or further comments?
Thanks!

Hardly ANY modern cars stall like this. This is not only aggravating, it is downright embarrassing!

have you replaced all your fuses yet? i had intermittent cold start problems this winter then one day my fuse #5 blew which disables the car. i cleaned out the fuse terminals with my dremel tool and a mini wire brush for the top part and a pointed brush tip for the bottom terminal. all my electrical gremlins have disappeared and haven't had a hard start since it happened.

No, I have not replaced the fuses, and that is probably a good idea on general principles, but it is hard to see how a fuse could explain the very consistent stalling at coolant temps below 80C. The fuse might be sesnitive to ambient temps, but not to coolant temps.
But I will put that on my list of things to do for the car anyway, and maybe prevent some other stuff.

That's what I thought too, but my starting problems have disappeared. I had thought about doing this before but since they all looked ok I didn't bother. The troublesome fuse was cracked and actually sparking. I also had problems with my cruise control which cleared up as well...

You may want to check/test your fuel pump relay. It sits right next to the OVP and controls power to the fuel pump, including pre-start energizing, idle and max rpm cut-out. While I don't want to encourage you to throw parts at a problem, I will say that my car had similar issues for a year or so, and since the relay was replaced I haven't seen them come back. I suspect time and/or poor solder connections caused intermittant open circuits in mine, though I didn't get a chance to look at it before I tossed the old part.

-anthony

A malfunctioning EHA could also be the culprit, although it is not common.
Hard start when cold could also be the cold start valve.
Stalling could be caused by a faulty fuel pump relay or fuel pump as well.
I was experiencing stalling when slowing down or turning. I cleaned the air intake and the stalling has not reocurred.

The fact that most of the cold start problems occur during moist, damp, days still leads me to rule out a fuel-related problem and focus on the electricals.

I am still thinking that the ignition coil (or coils) is the culprit.

there is a long list of possibilities. had same problem before
and replaced lots of parts - some necessary, some waste
of money. as i look back, i would recommend a good
fuel injection treatment - techron! pour two bottles in a
near empty tank and drive in low gear. good luck.

Ok, the 124 chassis CIS-E setup uses a ide speed control valve for idle. This is controled vis the CIS-E ECU. This valve is naturally closed during driving, there are 2 things I'd look at, 1) gummed up ics valve (just pull it off and clean it with carb cleaner by way of filling it, putting your fingers over the holes and shaking it, then dump and repeat until the carb cleaner comes out clear) 2) make sure the closed throttle switch is working and the linkage is making contact with it in closed posistion.


The ics valve is a tube mounted in front of the air horn behind the thermostat housing on top of the intake, retained by 2 10mm head bolts, 2 hoses and a connector. The closed throttle switch is on the backside of the intake in that nicely over engineered linkage, little black fellow with a connector on it and a silver arm on the side that the linkage depresses when closed, check it with a ohm meter, current flow closed, none open.


I had one that had rusted out the rear freeze plug in the intake that did wild stuff at idle as well look for vacum leaks, coolant temp sensor function and harness condition. The only real control for warm up fuel adjustment on this is that sensor. Once hot, the O2 comes into play. The rubber bottems of the airflow sensor will bust, ics bypass hoses will split and the vacum lines on the side os the throttle body will split as well. The vacum switch for the EZL advance control will fail as well causing minor running issues cold or hot depending on failed state. (function, cold no vacum pass through, hot vacum pass through) Located on the head near the ics valve.


Start/die on older 103's is nothing unusual when hot soaked however once running they should stay running.



Joe

Engine Harness
 

Try searching 300E's and 'Engine Harness'.

You will see a myraid of problems that are associated to the "Witch Hunt" you are experiencing. The harness was poorly designed and breaks down almost completely leaving cracked, dried out insulation exposing bare wires to the whims of Mother Nature. The harness plugs into the engine control box in the passenger side of the engine compartment behind the battery beside the OVP that you replaced. The other end feeds through to the various sensors around the back of the head and up to the front of the engine above the intake manifold.

I hope this will help you find your problem and I will monitor this post to watch your adventure.

Did the "coil" suggestion help? Faulty coil(s) certainly do breakdown at different temperatures.

I strongly agree with Joel's suggestion. My wife's BMW had the same problem and we paid mechanics more than $500 that did not fix the issue. A bottle of $15 Fuel System Treatment did the work. Good luck.

I have to also agree with Joel: It is a good place to start and certainly cost-effective. I have had good results doing this, especially with the high-mile 190E.

Haasman

Lots of good advice there, but the single most common cause of this behaviour is the fuel pump relay.

A friend of mine recently had an identical problem that was eventually traced to the fuel pump - it's poor performance was the cause of a weak mixture and bad O2 reading.

Check the warm up regulator

Next time it stalls try and open the gas cap. i had a 190e that had a pinched off breather line to the charcoal canister. After opening the gas cap the car started right away. then would stall later down the road. Driving with the gas cap off it didn't stall.

Problem diagnosed -- maybe
 

First of all, let me thank everyone for their advice.

Second, let me apologize for omitting what turns out to have been a key bit of information: My 300E is equipped with the ASR traction control system. I had not realized that would make a difference. But if my MB dealer tech is correct, and I think he is, the ASR was critical to understanding the cause of the stalling.

Unlike other 1991-1992 300Es with the M103 engine, a 300E with ASR has an electronic accelerator system. Instead of a conventional throttle control, there is something called the electronic accelerator pedal actuator. The “gas pedal” moves a potentiometer that sends a voltage signal to the electronic actuator pedal control unit. The signal is proportional to pedal position. The control unit determines how far to open the throttle, based upon the driver’s positioning the gas pedal but also taking into account the traction control system input (which can retard the throttle) and the cruise control function (which is integrated into the electronic accelerator control unit). The control unit sends a signal to the actuator, which in turn opens or closes the throttle. The control unit has other functions as well, including control of the fuel pumps (via the Engine Systems Control Unit, or MAS).
The actuator is essentially a (very special) reversible DC motor, which can open and close the throttle with both great precision and high speed (full open to full close in 120 milliseconds, or 1/8 of a second). The actuator also includes another potentiometer (to tell the control unit what the actual throttle position is) and a safety switch.
The safety switch is the apparent culprit here. The safety switch is part of a circuit that shuts off the fuel pumps if the throttle is open more than a small amount if the accelerator pedal is in the idle position. In other words, if the driver takes his foot off the gas and the throttle position does not follow immediately, there must be an error and the circuit shuts off the fuel supply.
According to the tech, there is a history of the safety switch “hanging up” or sticking, thus stalling the car. In my case, the sticking only occurs until the engine reaches a certain temperature. Since the actuator is mounted on the engine, it is sensitive to the engine heat.
I did a lot of reading about the systems involved here, and read lots of posts on this web site and others, before I became convinced that this was the correct diagnosis, but I did. (And by the way, the AllData site was very helpful in this regard, with good system descriptions that I did not find in the MB service manual.) One of the things that convinces me the tech is correct is that I can see the effect of the pedal movement very directly when the engine stalls. If I am going fast enough when it stalls (20 mph or so), the tachometer drops to zero but the car keeps moving without any indication from the instruments that there has been any failure. The tachometer signal passes through the MAS on its way from the EZL circuit to the tachometer. So when the MAS loses power, the tach fails. If I am moving fast enough (at least about 15 mph), and I push the accelerator pedal down again, the switch is again closed, the engine will re-start (from the momentum of the car turning the engine over) and I see the tach pop back up. None of the other instruments dies, no idiot lights come on, so the tach clearly has not lost power – it lost its signal, which can only mean that the EZL or MAS has lost power.
I can keep moving the pedal back and forth, opening and closing that faulty switch, and thus starting and stopping the engine, until I either warm up past the point at which the switch hangs up, or lose momentum so that a rolling start no longer works.
The parts are on order and the “surgery” is scheduled for later this week. Needless to say, the very special and sophisticated design of this actuator implies a high price, nearly a thousand bucks. And because so few 300Es have ASR, the part is rare enough it is not stocked in the US. So it is enroute from Germany. I will let you all know how it turns out.

Did this problem turn out to be related to the ASR as described?
Or was the crankshaft angle sensor the cause?

Check for bad spark plug wires.

Remove air filter housing and check the idle control valve hoses -- your idle control valve is sticking closed. The key symptom is stalling when coming to a stop only -- if it quits while running normally, it's the fuel pump relay or fuel pump(s).

If the idle control valves are rock hard, they are leaking. Check all the rubber vacuum line connectors, chances are they are bad too, and all your symptoms sound like a vacuum leak. Make sure the brake booster line is tight and the booster doesn't leak.

The rubber boot between the throttle body and the fuel distributor is probably bad, and check for leaks at the injectors with a bottle of carb spray -- while idling, spray a bit on each injector. If the idle changes, tis leaking air. Get new o-rings for the plastic sleeves the injectors fit in and change those, too. Best to do the injector seals, throttle body boot, and ICV lines all at once, as the injector lines have to come off anyway and the ICV line to the manifold is a real bear to change with the throttle body on.

Peter

Im guessing he hasnt checked this thread in 4 years

reply to the person from Australia
 

It was the ASR. Replacement of the motorized throttle actuator did the trick.

He still lives!

Thanks David!