Hello everyone, I have been chasing this hesitation problem on my 03 S600 for a very long time now and I lost all hope trying to figure out what it is and how to fix it. Its especially tough and frustrating when there are absolutely zero fault codes relating to it. I have pretty much run out of options, as I have changed everything I could possibly think of that this problem can be related to with no success. I am asking for help from all the knowledgeable people in this forum who may have a clue what it could be and how to properly go about fixing this nightmare of an issue.

The problem I am experiencing is that the car hesitates to move under any circumstance; whether it be at light throttle, medium throttle, heavy throttle, or full throttle. At light to medium throttle, the car attempts to move but the RPMs jerk back and forth, preventing it from taking off smoothly from a stop. If I press the gas pedal a bit harder, it moves past that "jerking" stage and gets going like normal, but it is very annoying and lacks smoothness, especially resulting in bad fuel economy. During heavy throttle or full throttle, the car launches forwards with incredible power until it hits a certain RPM - typically between 3.5k to 4.5k - and then the RPMs just abruptly halt and the car along with it, then the rpm climbs up very slowly and the car slowly accelerates following up with it, not giving it anywhere near its full power. The interesting thing is that if I put the car in 1st gear manually and give it gas, it has no problem and launches forwards without any hesitation (or none that I could immediately tell), until it gets to second gear and starts hesitating to put down the power again around that high RPM range. In addition to those two issues, there is another one that seems to be linked with them. When cruising at a steady speed or slowly coasting to a stop, with no throttle input applied at all, RPMs start to bounce back and forth between the 1k-1.5k range until I come to a stop or give it any throttle input. These three separate problems I have described seem to all be linked with each other as one huge problem, and I am confident that finding the solution for one of them will solve all three.

I have changed so many things on the car just in the past two months. I have been chasing this problem like a madman and I have not achieved any results because of its sheer difficulty of diagnosing. There is no check engine light. Scanners show nothing wrong with any systems. There is no trace of this problem ever existing within the car's computers. Therefore, I just started to throw a lot of parts at it, with no success. It has been a living nightmare. Here is the list of things I have done/changed on the car in the past two months with absolutely no result:

-Brand new coil packs, spark plugs, and red boot connectors (all properly installed with the proper OEM parts)
-Brand new fuel pump, fuel filter, and updated 5bar fuel pump control unit (OEM)
-Brand new MAP (green) and boost pressure (blue) sensors in the right places (OEM)
-Brand new charge air temperature sensor (OEM)
-Brand new accelerator pedal with sensor (OEM)
-Brand new PCV valve, oil separator, and hoses (OEM)
-Brand new vacuum lines for the entire wastegate/diverter valve system
-Brand new intercooler pump with a properly bled system, 12v always-running mod, and expansion reservoir (intercoolers are cool to the touch even after driving hard in California heat)
-Cleaned throttle body from carbon deposits, installed t-bolt clamps for boost hoses, checked charge pipes for leaks, changed air filters, no difference
-Rebuilt transmission valve body, along with upgraded torque converter lockup solenoids and springs, and changed fluid/filter

As you can see, I have pretty much changed everything that relates to vehicle power/hesitation issues. Although some of these fixes added some power back to the car, none of them fixed that RPM cutting off/bouncing/hesitating issue that has been plaguing my car. It has become extremely mentally frustrating for me, and I have used up all the information and resources that I could find from this forum, and none of it lead to me solving this specific issue thus far. The only other thing I can think of at this point is that the throttle body actuator itself is faulty, resulting in erratic opening/closing of the butterfly valve, but I am pretty certain that would throw a fault code. Another possibility I have in mind would be defective cats/o2 sensors, but those checked out fine when I had them tested. One more thing I can think of is that there is an air leak somewhere in the engine, but I cannot figure out where it could be coming from. Even if there was an air leak somewhere I believe my symptoms would be a constant decrease in performance rather than erratic engine speed fluctuation. So my money is on the throttle body itself at this point, but I do not want to just throw money at parts anymore with no result, so this is why I am asking all of you for your help and opinion. If my throttle body is the culprit here, what is the best way to go about fixing it? It looks like a basic Bosch electronic unit that is similarly used in many other makes and models, and I wonder if rebuilding it would be better than just finding a used one on ebay that may develop the same problem again later on due to age and use. If I do get a used ebay throttle body, will I need to program it to the car or is it just plug and play? Is there any throttle body reset/adaption procedure on this car? Any information or insight is greatly appreciated.

I noticed threads with complicated problems like these rarely have any videos demonstrating it, so I made one here just so everyone can understand what is really going on:


I apologize for the long and somewhat complicated post, but I would like this to be a main thread for people to stumble upon if they ever have the misfortune of being plagued with same problem. That way they would come here for a quick solution and be met with relief, since I was not able to have that myself.

 

I have experienced similar condition with my '94 SL-600 caused by defective wiring insulation in all the electrical wiring harnesses AND in the two throttle actuators. The surging RPM acts like the LIMP Mode RPM limiter. Why is that not setting a fault code? Cause the 'psuedo-limp mode' behavior is not triggered by the engine control module but by shorted wiring.
There is a 'guy' on the forum who is an expert in repairing the throttle actuators and EGAS modules and will also test yours on a real vehicle for a very very reasonable fee. Look him up and use his service.

(There is/was? a 'torque limiter' switch in the transmission in my '94 to protect that transmission from the massive torque of that V-12 that 'acted like' a RPM limiter with a hard cut/go action.
.
I am assuming you have already had a GOOD Tech use the STAR system diagnosis to try and find the cause. If not, do-so. Blindly replacing components can be fruitless and hugely expensive.
That the surging is persistent and repeatable is 'Good' because it means the cause is continuously in the wiring/electronics, and can be found.

IF the Techs using STAR cannot find the cause, I would pull the throttle actuators and EGAS modules and have "The Real World Expert' test/repair them to rule them out as 'the cause'..
Good LUCK and be persistent and methodical. The cause IS NOT intermittent and thus can be found.

 

Sounds like a tough one. V12TT problems often fit a pattern, but this sounds different.

Using a helper, with the ignition on but the engine not running, can you try observing the throttle position with the Y-tube intake off?

Nick

 

I have no idea why it isn't setting any fault codes. The wiring harness for the throttle body seems to be in great condition with no shorts at all, so I would rule that out. No STAR mechanics have been able to diagnose it yet and just dismiss it quickly, almost like they don't even want to work on the car. So much for running a business. My bet is that the throttle body gears are just worn out or the potentiometer is faulty and is sending wrong inputs back to the computer, causing the rpm surging. And my guess as to why the computer doesn't show any fault codes is because it thinks these erratic inputs are normal and doesn't "question" the surging as being a fault, but rather as what it thinks I'm trying to make the car do with my foot. It must think its user input, and therefore doesn't throw a code. I've heard faulty throttle bodies like this sometimes do not throw a code for these very reasons.

In that case, my next step would be to change the throttle body and see where that takes me. The throttle body unit that Mercedes uses for the v12tt engines is Bosch part #0280750125, but it is hard to find them new for a reasonable price. Doing some research, I came across a very similar throttle body unit that looks almost identical to the ones our v12tt engines use. It is used in a variety of Porsche models, and has the same exact mounting points as the v12tt throttle body. My question is, would this work with our cars as a plug and play solution or will the computer not be compatible with it? If it works, this would be a good option since its significantly cheaper and easier to find. If not, then I guess I have to either shell out $500+ for a new original unit or take a gamble by getting a used unit on ebay that may fail again in the near future.

Our v12tt throttle body:
https://www.ebay.com/itm/03-09-W221-...EAAOSwTM5Yuc6I

Porsche throttle body:
https://www.ebay.com/itm/Bosch-02807...cAAOSwbeBdBYd~

 

Try looking for a throttle body from a naturally aspirated sl600, cl600 or s600.

On both my V12TT's I fitted the gasket from the NA engine and it fitted right, so there's a good chance the TB will fit.

Nick

 

I feel your pain..

Do you have a scanner that can monitor values? Would be interesting to see throttle pedal and throttle valve position voltages in relation to each other. Does it do this stone cold start as well as hot and in closed loop?

 

It does it consistently, it is more noticeable when the engine is cold. Unfortunately I don't have a scanner (yet) that can monitor the throttle valve and sensor values, but I am almost certain that there is clearly an issue between the two trying to communicate and provide proper throttle input. It feels like it erratically opens and closes under certain circumstances, like when it does coasting to a stop or given light to medium throttle. And I feel like the butterfly valve gets stuck halfway through when given full throttle, explaining why the rpm cuts off at ~4k.

I also forgot to mention that the throttle response is very slow and dull now, it feels like the car doesn't respond to any gas pedal input in the first second. Jabbing the gas pedal quickly does nothing. It just feels like its not responding to my inputs how I want it to, and feels really annoying to drive.

Given these symptoms, assuming the throttle body itself is the actual culprit, what portion of the assembly could be faulty? Could it be the motor, the gears, or the circuit board/sensor? Is it a common problem for these to fail? I haven't seen anyone have the same issues I am having, especially on the v12tt.

 

Throttle pedals are known to fail on these cars, so if you want to change something I think that would be the first thing.

You could get more info by trying to replicate the problem under cruise control.

If can reproduce or observe the problem by manipulating the cruise control in some way, that would point towards the throttle and away from the pedal.

Nick

 

I already changed the throttle pedal with a brand new one from the dealer, that was not the culprit. The cruise control idea seems like a good one - I will try that out today and report back.

Is there any throttle body adaptation or reset procedure on these cars? I think the one where you put the pedal to the floor for 10 seconds with ignition on and then wait 2 minutes with the key in the off position is only for resetting the transmission shift points.

I will also take the plastic cover off the throttle body to inspect the gears, the spring tension for the butterfly valve, and clean the circuit board and sensor. If there is any difference I should be able to notice it. If that still does nothing, then I will go ahead and order a used throttle body assembly.

 

This might sound a bit silly, but...
Did you check your catalytic converters and or mufflers?

 

DO NOT 'tamper' in any way with the electronic throttle actuators. The gears NEVER wear or fail nor do the variable resistance films and gold wipers. Malfunctions are almost always (99.99%) in defective wiring/connections or the EGAS module power transistors.
Faulty mass flow sensor data will also put the car in 'limp mode' or limit RPM and power output. SOMETHING is causing the surging (throttle butterfly oscillating) and it CAN be diagnosed and fixed. IT MUST be properly diagnosed monitoring REAL TIME DATA to see what is causing it.It could be something as simple as a faulty Voltage Regulator in the Alternator, or a Bad Ground., or a broken wire in a wiring harness, or a bad connection in one of the many 'pins' in the connectors.

Dealer Techs often earn only a set amount (maybe only 1 hour max) for diagnosing electrical/electronic problems. They know it can take lots of time to find the fault. They end up working without pay on the job. Talk 'turkey' with the Service Manager--the person who is responsible for the Service Dept about the non-response, etc. Get MBZ USA involved as well. THEY WANT your car fixed. They WANT to figure out what is causing the problem. They may have experience in resolving the identical problem. Paying for a real good diagnosis using the STAR, DAS, and WIS programs IS the way to go. Blindly chasing and replacing parts is usually NOT productive in these kinds of problems.

 

Thank you for the information. I usually avoid doing any sort of business with stealerships, I would much rather prefer a private individual who has a lot of knowledge and the right equipment to diagnose a problem like this. I have done all that I can possibly do myself. In that case, is there anyone in southern california that is up to the task? This problem seems much more complicated that it really probably is, and I would be relieved if it just ends up being a bad connection somewhere.

 

There is an old axiom about horses and watering troughs that seems to be appropriate here. MBZ corporate techs ARE THE BEST and They have all the latest and best information on problems like this. There possibly IS someone who does have/know exactly what the problem is--but finding them close is a needle in the haystack problem.
Good Luck and keep sharing with us.

 

Just get a pre buy inspection from a real Mercedes Dealership. Mine was like 220.00 (A little over an hour back in 2014. Current price is 185.00 an hour) bucks at the House of Imports in Buena Park California.

They will tell you every last thing that is wrong with your car.... In your case be prepared for maybe 2 hours.

Once you have the correct information, then you can go "fix it" yourself.

Just and idea...

 

If you plan on pursuing this problem yourself a scanner that can read values is invaluable. The icarsoft unit will do this. I have this for my 2006 S600. I got the $400 one that will read all modules from all manufacturers. As far as engine data goes I'm not sure if it shows more info. than the cheaper generic OBD one, but it sure does have a lot. Mine isn't a full function unit though as it is very limited as far as it's resetting capabilities. It will however perform throttle adaptation. It is also nice to be able to access and read data from ALL the modules on my car, as well as anyone else's.

 

Will that one do offline programming?

 

No. This is a low level scanner, my $400 version anyway.

 

Ah, okay. Thanks.

My Star C4 cost about 400.00 as well.

 

So I tried doing the cruise control thing, and the rpm still fluctuates at a very specific set speed. It does the same when not on cruise control, it only occurs at the right "window". Just a little bit less or more throttle will stop the fluctuation. It only does it at a very specific "point" in the gas pedal, and is very easy to replicate.

Every single time I quickly stomp on the gas pedal, whether it be medium to heavy throttle, the power just immediately cuts off and the engine stops revving up. If I continue holding it, it revs up very very slowly. When I let go, the car doesn't go into any sort of limp mode, nor does it throw any CEL, and it continues to drive normal as long as I don't give it heavy throttle input.

Clearly, the computer is cutting off power for a reason, but I just cannot figure out why. If I put the car in first gear manually, and gradually press down on the gas pedal (not immediately), it takes off just fine as seen in the video.

The previous owner did do an ecu upgrade tune back in 2011 with an unknown brand, but I have no idea if it's still on the car or not. Can this power cut off be caused by a bad ECU map?

Is this power cut off problem even related to the bouncing rpm problem?

 

At this stage of your investigation, it certainly is worth a good 'Pre-Purchase' diagnosis with STAR, DAS, and whatever else a Dealer Tech can use. Tis time to get MBZ corporate in the hunt.

 

They don't just use Star..... It's a something something point inspection. The car is put on stand and every inch is gone over. Provide one goes to a "Real" Mercedes Benz Dealership. Mine was something like 20 pages and a total of $13,000+.
I think $9,000 in just labor. Good thing where the car came from had 100 percent warranty for 30 days, so they had to fix everything on the list.

 

Hey Guys.

I am using W220 2001 from last 6 years with no issues at all.
now at once i am facing this issue. When ever i go through any jump or any broken road with just 20KM/Hr speed or above the power fluctuates like everything goes off and comes back immediately.
does anyone know about this issue.Please do let me know. waiting for reply

And sorry for replying here. couldn't find the button for new post.

 

For a very quick 'bump triggered' self healing shut-off. first place to look is the main power supply connections---such as connections on-to the battery, and then a good test of the battery.
Broken connections (cell-to-cell) inside the battery are not unknown. If those are good, then the relay connections providing the ignition system power. Then the power supply to the the key system. Somewhere is a loose connection/bad relay. Ground connections are notorious. Many 'better' scan tools ($250 +/-) can test each connection and circuit without you having the physically locate and probe. (I would hate to undertake a manual locate/test with VOM)

 

Ok, so I took the car to a Mercedes technician and had the entire car scanned with STAR/DAS for any error codes relating to this engine power cutting off/fluctuation issue. The only thing that was found that could possibly be related is a cylinder 8,9, and 10 misfire. Nothing else. I am really confused at this point. I have changed all 24 spark plugs with NGK IFR6Q-G, replaced the coil packs with rebuilt units by Clark at v12icpack, changed the valve cover gaskets to ensure no oil fouling, and pretty much did everything else that cures misfires on these cars. And it is still misfiring for some reason. And now it is apparently correlated with this other issue I am having.

I asked the technician what the misfires could possibly be from, since I changed every damn thing that is related to it. He said it could be from a bad coil pack which wasn't rebuilt properly, or that the intake/exhaust valves in my engine are burned up or have excessive carbon buildup, which prevents the valve from closing properly during combustion and causes a misfire. He said this could explain the power cutting off/fluctuation issue, since the engine is trying to make power but the valves are not sealed properly and causes the engine to react this way without throwing a CEL. I don't think this is the case, as I take everything Mercedes technicians say with a grain of salt. If it were a bad valve then I believe smoke would be coming out of the tailpipe, which it never does.

So there are two big questions here. Why the hell is the car still misfiring? And are these misfires actually related to the power cutting off/fluctuation issue? I've never heard of or seen anyone here who has had the same symptoms I am having with the engine power fluctuation, and it turning out to be because of misfires. No one else with misfire issues on these forums have ever described these symptoms, so I am doubting the correlation. Some experts really need to chime in on this. It would be very, very much appreciated.

What do you guys think. I'm stumped at this point. I'm ready to give up and just deal with the problem.

https://cimg7.ibsrv.net/gimg/www.mbw...160fd2513b.jpg
https://cimg8.ibsrv.net/gimg/www.mbw...f588ace215.jpg
https://cimg9.ibsrv.net/gimg/www.mbw...cec501302a.jpg

 

I have some vague memories of discussions about some red rubber inserts on the ignition wires that need replacing to cure misfiring.