Jarbra

Hello from Norway! I am x-posting this from the C219 forum, as the platforms are the same. Link to original post.

I have a 2005 CLS 55 AMG where I have a very annoying problem. The car has now traveled 29,000 kilometers (18.000 miles), but the problem has been there since I bought the car with approx. 21,500 kilometers (13.350 miles). But I think the problem has become more pronounced lately. The symptoms are as follows:

-Sometimes the car feels fine, other times the faults are very obvious. The error is therefore periodically worse/better. I have not been able to identify WHAT is decisive for whether the error is there or not. Sometimes I have been able to drive long distances without problems, other times the error is there from the moment I start the car.

- It seems that the lockup in the torque converter is disconnecting very hard and brutally. This feels like a hard gear change. Typically if I'm in 80 kmh (50mph) and get into a 60 (40mph) zone, and it's a bit uphill.

-It can seem that the lockup sometimes cannot decide completely whether it should be on or off.

- When I'm at a steady speed, for example in a 50 zone, it can "jump" or buck. It feels like variations in available power that I have to compensate with the gas pedal. It can almost seem as if the engine or the car is running hard.

- When driving in queues, it can "jump"/buck or chop. You can feel it throughout the car.

- The car feels "bumpy" in the distinction between engine braking and gas application, when rolling downhill. It can also feel like it is bumping a little when braking on the engine brake.

- It is difficult to describe, but it can almost seem as if the lockup occasionally "hangs on", so that the gear and engine are locked together. If I give the gas suddenly, or release the gas suddenly, it sort of slams though the driveline. The lockup should from what I understand almost always slip a bit, but it feels like it is being applied too much at the wrong time.

-When driving hard, the engine runs well and has plenty of power.

I have done quite a bit with the car so far, both preventively since the car is, after all, 17 years old, and something in the hope of rectifying the fault. What has been done:

- Replaced MAP sensor
- New intake temperature sensor
- Bosch 010 pump
- New crank sensor
- New cam sensor
- Changed all the injectors, with new o-rings and a new pulsation damper on the fuel rail
- Changed both fuel pumps and fuel tank gauge (there was some sweating from the tank gauge anyways)
- Tested with a different (used) throttle body from my SL.
- Changed the conductor plate and connector in the gearbox (here there were error codes on the speed sensor), had the gearbox serviced and replaced PWM solenoid for the TCC with a new one. There was oil in the connector, but not up at the TCU.
- Replaced engine and gearbox mounts.
- Replaced front lambda probes/oxygen sensors.
- Replaced TCU/Gearbox control unit. This has modified software from TJ Merry. But made no difference in terms of the problems.
- Put over all coils and plug cables from SL.
- Spark plugs have been changed.
- Also it has a Quaife differential. No change because of this.

A new consumer battery was inserted when I bought the car, as the old one was dead. And probably something else I can't think of on the fly.

At the time of writing, the car has no fault codes stored, neither on the gearbox nor the engine. As mentioned, there were error codes on the speed sensor in the conductor plate, but this has not returned after it was replaced.

I visited a transmission specialist, they took part in a long test ride and felt these hard "gear changes". They believed that there was most likely no mechanical fault with the gearbox or torque converter. They believed that the lockup receives a signal to fully open from the TCU when it really shouldn't, and that this could be due to the TCU receiving the wrong input from the engine control module. I also think it would be strange if the gearbox was worn out in any way, as the car has hardly been driven. The fact that the error is intermittent also leads me to believe that there is some electrical or sensor problem somewhere.

I also spoke with another specialist shop. They had experience with a similar problem, where they overhauled the entire transmission and changed the torque converter, but that did not solve the issue. Therefore they were not very eager to help, but at least it strengtens the theory of something electrical being the issue.

Other observations I have made:

I have checked the ECU connector for corrosion/oil but looked very clean and nice. I have measured the intake vacuum (20 in-hg) and looked for vacuum leaks without being able to find anything. I must have emptied two cans of starting fluid into the engine compartment without being able to find any leaks... It doesn't really look like the engine is missing, but of course it is difficult to know whether the fault is in the engine or gearbox.

The engine has, as you know, an electromagnetic clutch on the supercharger. It seems to me that this is activated by the ECU too often. When driving at a steady pace, this should be disconnected, but I read from the values on my diagnostic tester that this is "on" also when driving nicely. I think this strengthens the theory that there are some wrong values somewhere, and that the motor may be registered with a higher load than is actually the case. But it is also possible that this is a dead end.

I also have an SL 55 with the same engine and gearbox and it is not like this at all.

Hopefully you understand my english and descriptions well enough. I have of course searched this and other forums extensively, but have not find a solution that I have not already tried. Looking forward to hear from you guys!

Additional info gained after posting:

- Sometimes the interior and exterior lights "pulse". new voltage regulator is on order, but I doubt that this is the source of my problems?

- Its hard to explain, but kinda feels like the car "bogs down" a little bit when upshifting.

Jarbra

Bumping this one. I changed the voltage regulator, and the pulsing lights stopped. No change in the problems though..

I also tried cleaning the connectors for throttle body and bypass valve, but the problem is still present.

I would really appreciate any help!

radride

Has this issue just started or was it there when you bought the car? Is the car stock?

R.K.

Jarbra

The one that was there when I bought the car was original. I myself have changed it out for a new Mkultra one. The problem persists with both TCUs. I also have a Mkultra in my SL55, and this does not have the issue.

machild

Maybe Steve will stop by and have a thought @SICAMG

Jarbra

Ok, so I have an update. I have tried updating the ECU, no change. Changed the gas pedal (TPS), and the throttle feels better, but the problem is still there. I even had an ecu specialist open the ECU up and check it out, but he could not find anything wrong.

But I noticed that the gearbox temperature seems very low. After driving for 22 minutes at different speeds, it reads about 40 degrees C (104F) with Xentry. And after driving in queue for 35 minutes it only goes up to about 50C, (122F). This seems very low to me. Even after doing some hard pulls on the freeway it stays very stable around 122F. Has anyone experienced this?

nd-photo.nl

It should be higher indeed, I believe somwehere around/above 80 degrees celsius.

Might be a temp sensor issue? Although I have no idea where the temp sensor for the gearbox is mounted...

Jarbra

I think so too. I'm pretty sure the temp sensor is in the conductor plate, which is new..

nd-photo.nl

I was fiddling around in the garage with the Airmatic height and was able to get you some info. This was after 20 mins of idling or so (in neutral)

Jarbra

Thanks for checking, unfortunately that is the engine temperature, as the gearbox is in N. It has to be checked in D og R.

You can see the temperature change if you take it from N to D. That’s because the temperature sensor is connected in series with the lockout switch.

nd-photo.nl

Ahhh ok, I will check that today.

I thought it wouldnt show anything unless you put it in D or R.

Jarbra

I really appreciate that, thank you!

Yeah, you would think that it would not display anything, but according to DAS it displays engine temperature when in P og N, since signal power is not provided to the temperature sensor in the gearbox.

nd-photo.nl

Well learned something new today, thanks @Jarbra I saw the value changing when putting it in D or R.

This was after about 15 mins of easy driving, with about 15 C ambient temp

Jarbra

Thank you so much, man. I really, really appreciate it. Then it seems there is nothing wrong with the temperature reading. Here it's about 0-5C these days, and my readings are not that far off yours.

I have ordered an automotive smoke machine, and will use it to search for vacuum leaks on the intake system. I can't really think of anything else to check now.

nd-photo.nl

You are very much welcome

SICAMG

Hey man did you clear out the adaptives and then drive it?
I would do this and drive it back to back. This will give you a very good unbiased view of what is going on as far as the ECU/TCU inputs. If there is a big change when performing the road tests than we can go from there.
Many times when trying to isolate an issue with the trans and you clear adaptives the first 1-2-3-4 shift will be on it's own so to speak with no "adjustment/ control " to speak of from the TCU. As you keep driving the learning process starts and the problem begins to be adjusted out from the ECU/TCU and becomes more and more pronounced. Or...it could be the opposite.
So long story short, clear adaptives,drive it,see what it does and see how it begins to "change" from the ECU/TCU trying to get things where it wants it.
If you clear adaptives and it is far worse then we can go down that rabbit hole.
I can also tell you the temperature plays a big role with the shifting on these transmissions as well but lets see what it does after the test's.
Gary

Jarbra

Hi, SICAMG!

Sorry for the late reply, I didn't get a notification that there was a reply.

I'm pretty sure it's not adaptations, or that clearing them will give any clues, as I have changed the TCU to a fresh Mkultra one, as well as cleared adaptations on the ECU (even updated it). And also the problem is intermittent, occuring on irregular intervals. Sometimes the car drives smooth as silk, other times it feels crap from the get go.

I got to test my new smoke machine today. No visible leaks on the intake side. So now I'm stumped again, and have run out of things to try..

SICAMG

Im pretty sure you can shut lock up off with Star and road test again. This way if the problem goes away you for sure know its the converter.

Jarbra

Thanks for the tip, I will try that. However, the problem is also present in speeds below lockup engagement (like driving in heavy traffic, almost standing still). So if the lockup still engages somehow when the TCU tells it to open, then I doubt disabling it in Star will help. It's hard to describe, but the gas pedal feels jerky, and it's almost like the load calculations are all wrong.

I feel that the only thing left that I haven't tried with the engine is to change the electronic bypass valve. Thought I have tested it with Star, and it seems to work fine. But like I said, the problem is intermittent, so perhaps it was just fine in the moment when I tested it.

SICAMG

Not the bypass as blower is not engaged when crawling through traffic. Also shutting off the TCC WILL cancel all electrical control of the converter so if it still feels like it comes on then it's a converter issue and that is what I am leaning towards. You will get a bucking ,notchy feeling when the converter is locked solid and trans up shifts/down shifts. You will have a constant connection with the engine, just like a stick shift.
I wish you were close by so I could drive it and see for myself.

nd-photo.nl

Norway is a nice place to visit im sure of it

SICAMG

Im sure it is. I just came back from Iceland and that place blew my mind !!!

Jarbra

You are welcome here any time!

I have an update, sorry for the late responses! I tried disabling the TCC, and the car felt MUCH better! I have to test a few more days, but I think this actually might be the issue.

It seems the lockup "drags" too much, or is applied too much. Perhaps the friction in the clutch plates is too high or something similar. I already changed the solenoid, so I suspect it's the entire converter that is broken.

SICAMG

That's what I suspected. Probably needs a new converter but if the trans is coming out then go through the trans as well.

Jarbra

How is it even possible for the torque converter to fail with such low mileage? The car is imported from japan, and seems to be driven very conservatively.

I guess I’ll have a weekend on the garage floor ahead of me!