1995 E320 - Engine missing badly during acceleration
 

I have a 1995 E320 W124 with 119K miles. It started a few weeks ago, but it only seemed to happen when the car was cold. At first I was thinking maybe it had something to with the choke fuel mixture controls. Yesterday it was pretty bad even after it warmed up. When I push the gas the car just kind of sputters until it finally takes off more or less like normal. To me it feels kind of like the spark plugs may not be firing or like when an engine is being flooded with too much fuel to burn.

This may be wishful thinking, but I'm hoping maybe this is common if it has been a while since the plugs were changed. I have to admit that some of those routine things that were done routinely at the dealer have become only as needed items at my Indy. Something is definitely needed now. It has been a while since I did any engine tuning maintenance things. No warning lights are showing on the dash.

I will be making an appointment ASAP at my Indy, maybe even today, but I was hoping maybe someone here would give me some hope that this is likely only a minor issue and suggest a path forward.

ksing44, my guess would be that the rear-most coil pack is bad ... had a similar experience with our 1995 E320 (which I diagnosed and repaired myself via trial & error by installing a new coil pack in each of the three positions). I'm sure Rex Carle's shop can quickly diagnose and repair the problem.

Thanks Fred
 

I've been going to K&S Automotive, even though they are not Mercedes Specialists like Rex. I just really like and trust the guys and liked and trusted their dads before them. I hope they can figure it out too. I will give them your suggestion.

Thanks again,

Ken

I had a very similar problem with my 94 E320 Wagon. It also turned out to be a bad coil. Mine was a bit difficult to diagnose because no codes were present. I know there was a production run of coils with a rather high failure rate, I'm not 100% sure but I think they are identifiable because they are blue in color. Another common cause for misfire is the coil to plug connector, lots of searchable information on this. As always, posts by Arthur Dalton are always spot on. Fortunately, niether of the above are very expensive, coils are about $75 from our site sponser, plug connectors are less than $5. I would think not more than 2 hours labor would be reasonable for diagnosis and repair.

Coil pack failures are not common.

Most likely, the plug wires are aged. Mine did the same thing, and fresh wires did the trick.

Bad plug wires will cause other issues, such as plug fouling and O2 sensor failure (which occurred as a result of the bad wires).

<Coil pack failures are not common.>

Want to a waste basket full of them..
VERY common on HFM/SFI Waste Spark/DIS Ignition systems.

But more probable is the 3 plug connector/resistors under each coil.

Well, you would know from experience, but my coils have been through a lot of abuse (e.g., water, after washing motor several times), and despite all of that, always tested fine.

I figure the plug wires will eventually succumb to age, whereas the coils are a more expensive proposition if you are just swapping them out without knowing which one is bad...

Yes, I would know.

Waste spark coils were so notorious that they changed the design 3 times.
B/c yours are not bad is not a reason to post that they did not have a common problem with them, cuz they had plenty of problems ..ask anyone who had the Early Blue ones....NOTORIOUS
...and we do not swap out ANY parts until we know they are bad.

For the OP, how about the wiring harness? Outer sheathing disintegrates because of heat. Known item to go bad, expensive part last time I checked!! Hope it turns out to be something cheap and simple like a coil pack.
Regards,
Jerry

Thank you everyone for your help
 

Today my car ran much much better. It was hot and sunny, but yesterday is was raining. That dramatic change from moisture makes me think it is electrical. I remember the old days and having to remove and dry out a distributor cap. I just hope it is easy to diagnose, even if it isn't acting really bad when I take it in to my Indy on Wednesday. That was the earliest they could see me.

I'm going to be fixing my car up a bit to let my son have it. That way I don't actually have to part with the car that I have loved all these years. It will just be driven locally.

Actually, I quoted my indie on the coil failure issues based on his personal experience...since I only tool around on my own vehicles, I don't have enough background history to dictate what is and what isn't normal...should have stressed that from the start.

And I know you personally don't just swap parts out...I was referring to the premise of which is cheaper if one was to go about diagnosing a problem by doing just that. Sorry for the misunderstanding.

Ironically, now that ksing44 mentions improved performance with the weather, it really does point to coils...a corroded primary terminal on my VW coil gave me the same grief during moist weather...no issues when sunny.

My '95 E320 was doing the same thing at 100,000 miles. A change of plugs, O2 Sensor cleared it up.

<<a corroded primary terminal on my VW coil gave me the same grief during moist weather...no issues when sunny.
__________________
>

Yes , moisture is nasty on any cars secondary ignition system

An old trick we used to use if the car was having a hard time starting/runnng in rainy weather was to coat the wires with a quick spray of WD-40,,if the car started right off, we knew the wires were junk..WD is a Moisture displacer [ Water Displacement is the WD part]
But on the Waste spark , I agree that first suspect before coils is the coil to plug connectors under each coil...they are very common, to the the point that most Techs will change then at each plug change b/c of their known fail rate..but the waste coils are still high on the list, mostly due to the fact that they use One coil to fire two cylinders , in Series ..us they are heat trapped with their location...
Anyway..if one does suspect a failing coil in these systems , by moving the suspect coil to another location and seeing if the misfire follows the swap is a cheapo diagnostic trick for the DIY who has no Scope, etc...that is a diyer way of part failure confimation before purchase.

When my indie was diagnosing my misfire issue, he noted that when plugs were pulled, two of them (from the same coil pack) were fouled. So he changed all plugs and swapped coils to see if the problem would travel to the suspected defective coil.

I drove the car for a couple of weeks.

When he pulled the plugs again, the same two were fouled, despite the coil swap. That led to the conclusion that it was bad plug wires, not coil. Replacing wires cured the misfire in my cases, but unfortunately, collateral damage had already manifested in the form of a fouled catalytic converter and shot O2 sensor.

I suspect that I am eventually going to lose the coils considering they are original...

<
When he pulled the plugs again, the same two were fouled, despite the coil swap.>


Yes, that is why we always change the resistor plug connectors under the coils first.....and everytime the plugs are changed. One bad Coil Connector effects both plugs on that system b/c the plugs are wired in Series.
The problem is the connectors under the coil are a spring contact, whereas the other plug in that series has a much better snap connecton.
They are a maint. item and last about 50K. As they age , they burden the coils, with the main fear of taxing the trigger circuits in the ECU. Being a DIS system, all switching is done at ECU and to tax that can be very costly..so, the connectors under the coils w/plug change is cheap insurance.
Plus, a large percentage of mis-fires on DIS HFM systems is those 3 connectors. It is always the first recommend when misfire is the condition. If coils are suspect on that chassis , one simply goes into pin #8 of the Module and looks for a 21/22/23 codes ..those usually pop with a coil malfunction..it is after we see that , that we do the swap and then simply go back and see if , for example, if a 22 has moved to a 23 ..then we know right away the condition has followed the offending coil..no driving around for weeks and looking at plugs ,etc..

I have 88 w124 coupe with 103 engine. I experienced a similar problem. No acceleration when initially stepping on the accelerator. Motor would sputter and spit the eventually accelerate normally. Sometimes it would sputtrer and spit and I would have to pull over. I read a thread about adjusting the air/fuel mixture on another forum. On my car there is a small cylinder on top of the fuel distributor which on most cars is covered by a small ball. Mine had been removed. You need to remove it. You take a 3mm allen wrench and insert it into the cylinder while the engine is running. If you push the wrench in too far the engine will stall. You need to feel the wrench engage and turn it left to lean right to rich. Probably left to lean to correct your symptoms. The correct method on my car is to use a multimeter an plug the positive into #3 port (positive) and ground the other wire on the meter. You should try to set it at 51%. However you can put the coon tune on it by just experimenting with small turns in either direction. ie= turn to left a little- drive it. etc. etc. My car has Ktronic fuel injection system. I don't know if this applies to your car but I did this prior to buying and replacing parts and it fixed the problem.

Side note
 

I saw that you are from Dowingtown, PA. My father is from Dowingtown. We used to go there every summer to visit his mother and his sisters family. My dad was captain of the Dowingtown High School Football team in 1935 or 36. Good luck with your car. I did change spark plugs on my car before adjusting the air/fuel ratio but there was no change in performance.

Wiring harness is the most likely culprit if it hasn't been changed....change it !!

I just wanted to let everyone know that a “complete tune-up” seems to have completely resolved my issues. My Indy provided new plugs, wires, air filter, fuel filter, and cleaned the injectors. My car runs great!!!

They were so busy that I wasn't able to discuss things with them to determine if they checked other things, but my car seems totally fixed for now.

I graduated from Dowingtown High School in 1974, so your dad was before my time. My son goes now. This is a nice place to live. It is a beautiful green rural setting, with great access to big east cities and to the coast. We don't have too much severe weather, like tornadoes or hurricanes. We also don't have huge fires or earthquakes. All in all, I think this is a pretty great place to live and work and raise a family.

I like mine, too. After my new O2 sensor and plugs, I started getting the Check engine light. Arthur helped me troubleshoot, and ended up that reseating a few vacuum lines cleared that up. Now the car runs really well. As I now have a) new wiring harness, b) new head gasket and c) new AC evaporator car I hope to drive it another 100,000 miles.

Wow, you really are committed to your car, or maybe you should be committed to an insane asylum. Actually, it probably will go at least another 100K. I go back and forth almost constantly about spending more to fix things on my car. For now, I am still just fixing something if I absolutley have to do it to drive the car.

Good luck with your car

Probably a little of both. Actually, previous owner did the wiring harness, and I bought the car knowing the head gasket and the Evaporator would need replacing. Price was discounted accordingly. I bought it from an MB dealer that had taken in on trade, and wanted to move it. They gave me a good discount on the head gasket. The evaporator core was done by my independent, again with decent discount, and I gave him plenty of time to do it. The reason I like this one is that the interior is perfect, not even a crease in the front seat leather, the exterior is near perfect, and there is absolutely no rust. Given all of this, I don't really have a lot of money in the car and hope to have it around for quite a while. My independent has been all over the car and says there is nothing else needed. Certainly would be hard to replace at anything near the $$ I have in it for anything better (IMHO) - and in this case, I know the big stuff is done, and was done right.