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Topic-icon Engine Problem

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16 Jul 2017 18:26 #7842 von rsadut
rsadut erstellte das Thema Engine Problem
Hi

I have a problem with my engine.
No mechanic seems to be able to find a solution.
The car I have is C107/107023-1972. 3,5L V8. Motor 116.982. My problem is: at certain engine speeds the rpm drops drastically. i.e.: ca. @2700-2800 rpm at steady throttle it drops to ca. 1500. The same is repeated while driving. when the rpm drops I hear explosion sounds from the exhaust. Only when I depress the throttle further or decelerate by pulling my foot back the engine starts to rev up again and goes back to normal rpm starts to increase again. Sometimes I feel the same @ ard. 1700-1800 rpm and above 4000 rpm. The amboss( has been replaced with a new one from MB just recently. I have had the injectors cleaned last week (0280150034). out of 8 four are working with similar performance. two produce a higher output (+2-3 mg) and the other two are performing a bit less(-2-3mg). after each replacement all adjustments are made again. nothing changes. the last mechanic even tried different ecus one from 280 and 350 and man. Pres. sen. The fuel pump was recently replaced as well. I have continous pressure at all rpms 2.00 bar. the problem is there but may be softer. there is a cyclical repeat of this problem it reaches its climax at the high end of the torque. d-Jet parts match, pcb of ThPoSn. has been replaced with a new one. MPS was overhauled at Bosch(part bob). electrical wiring has been renewed incl. all connectors. I am a bit helpless. Would appreciate your contributions. You may reply in German. I can send a sound/video file
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16 Jul 2017 19:50 #7843 von Volker
Volker antwortete auf das Thema: Engine Problem
Hi,

that seems indeed a tricky issue. Even if you have replaced ECU and MPS with 350 compoents (280 does not fit!) and it still ist the same. Even new TPS. Did your mechanic measure both temperature sensors cold and warm? I guess so.

Waht are possible causes provided with all the things you have already swapped:
  1. fuel pressure decreases at this speed. Connect a pressure gauge with a 2m hose and tape it wo wind shield. Does fuel pressure decrease at these speeds?
  2. Sometimes we have seen loose trigger points. They should not moe at all when you try to do so.
  3. If not we could still have a cabling issue

Viele Schraubergrüße - best regards, Dr-DJet Volker

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16 Jul 2017 21:07 #7844 von rsadut
rsadut antwortete auf das Thema: Engine Problem
1- Fuel Pressure: On Friday I was at my mechanic. a manometer was attached to the fuel 'Ringleitung'. The injectors were not cleaned yet but the necessary adjustments were already made. at certain rpms we could hear exhaust explode and engine was stalling but pressure remained stable at all times. therefore I would exclude this possibility but another test can be performed.
After that my mechanic concluded that the problem should be with the injectors. This is why I spent the next day removing and cleaning injectors.
As the problem continued after cleaning I decided to consult the forum.
2- Loose trigger points: what do you mean by loose trigger points? I bought a brand new amboss by MB. Nothing has changed after the exchange. I had also adjusted my old one with your Gebisswerkzeug. I also check the positioning before installing the new one. If you mean the Zündverteiler' s shaft is moving loose and the injectors fail to receive command how can I check this? Why would the problem go away when the throttle position is changed?
the cables from the Zündverteiler to the spark plugs and the coil have been replaced with a new set.
3- for the combustion to happen we need spark, fuel and air. Considering we have the spark and the fuel (they are both operated by the ZV) what about the air. Could reduction in the amount of air cause such a problem? i.e. when the Zusatzluftschieber hose is pressed the engine rpm drops?
4- What should I check about cabling? I have all the wiring diagrams from ecu to sensors
5- would it make sense to gradually remove sensors like the MPS, Ansauglufttemperaturfühler, TPS, etc.
I would like to repeat again that engine is not stopping or trying to shut down it slows down asIf it is being choked.

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16 Jul 2017 22:19 #7845 von Volker
Volker antwortete auf das Thema: Engine Problem
Hi,

I would like to greet you with your name, but that would need you to sign with your first name.

Exhaust explosions normally mean unburned fuel in exhaust. That typically happens with improper igntion voltage or timing. I would recommend you to check igntion timing at idle, 1500 and 3000 rpm comparing to workshop manual values.

Fuel pressure could change if fule lines are somehow blocked. That is why I asked to check at all rpms.

Even brand new trigger contacts can be misaligned or be loose. I recently had two loose screws under the soldering points.

Missing air cannot be the problem as you deliver it via throttle. AAV can increase rpm but not drop it if it is closed.

If you remove MPS it will stall the engine. ECU needs MPS to operate.

Viele Schraubergrüße - best regards, Dr-DJet Volker

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16 Jul 2017 22:31 #7846 von rsadut
rsadut antwortete auf das Thema: Engine Problem
Hi

My name is Juan. Thank you for the suggestions.
I will check and will revert to you

Rgds
Juan

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17 Jul 2017 01:48 #7848 von nordfisch
nordfisch antwortete auf das Thema: Engine Problem
Hi Juan,
be very careful... backfiring can kill the diaphragm of the MPS.

You said the TPS was revised with a new PCB. Maybe the contacts for acceleration (at the rotating unit) or the PCB itself / the sleeve contacts were greased? Don't grease these parts, just clean them. They won't give any contact if greased because the electric current is very low.

Did you check the clearance of the engine valves, inspected the engine camshafts? I don't know, maybe your engine has "Hydrostößel" (don't know the word, 'automatic valve clearance setting')? Can get defective, too.

But please begin by checking the ignition as Volker wrote before.

You asked if it's possible to remove the sensors.

You could replace the two temp sensors with fix resistors, both 200 Ohm, min. 1/4 Watt for testing.
This would simulate normal air temperature and warm engine.

Removing the TPS electrically would mean missing idle signal / no stable idle, going up and down.
No impulses when accelerating = problems in accelerating will be the result.
But: No problems should occur in constant driving conditions, ignition is regulated by the MPS signal then.

Regards
Norbert

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17 Jul 2017 20:46 #7852 von rsadut
rsadut antwortete auf das Thema: Engine Problem
Hi Norbert,

Thank you for the tip about backfiring. Actually I drive my car only from mechanic to the garage as I do not feel comfortable driving the car in this condition. Intry to set the speed to avoid the problem.

I did the exchange of the TPS and did not use any grease at all. The contacts are dry. The old unit was also in good condition but someone had suggested that worn contacts may cause such misfiring problems. Therfore I found this gentleman in NL through the net and ordered the piece.

I did not check the clearance of the engine valves and inspected the camshafts. I need yo consult my mechanic. Is there any literature I can read or ask SL club to provide from MB?As far as I can remeber the chain was replaced, several other parts were changed but I do not remember. I need to look it up.

I am also a member of the 107 SL club. I have access to the EPC. I can check If my engine type has the Hydrostössel.

There is a camshaft like part inside the ZV. that is creating the signals. Can it become loose after a period of time? Could it cause such problems If it does not spin properly?

I will do as Volker has advised.

All engine mechanics I have known work with the motor while idling and mechanically try to simulate load by manually adjusting throttle on the engine. This problem is audible during all these tests

Thanks again for all the advice.
I will keep you posted

MfG aus Istanbul
Juan

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17 Jul 2017 21:24 - 17 Jul 2017 21:31 #7853 von nordfisch
nordfisch antwortete auf das Thema: Engine Problem
Hi Juan,
you find everything you need on top of this page "107 workshop manual".
oldtimer.tips/en/107sl-wsm/107sl-wsm-con...7sl-ri-engm-m116m117
05-210 to 05-215
But a mechanic doesn't need this to inspect the camshafts for wear. My own car (Opel, no Mercedes) started backfiring when 5 of the 12 cams were almost gone. Had measured engine compression before inspecting the camshaft without great abnormalities.
The 'Hydrostößel' corrected the wear until the valves didn't open any more.

The engine had a decrease in performance (no more then 150 km/h) - but was still driveable, many hundreds of kilometres up to the time the same problems you described occured..

But check the ignition first... hope you have another problem than I had.

Regards
Norbert
Letzte Änderung: 17 Jul 2017 21:31 von nordfisch.

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17 Jul 2017 23:08 #7854 von Volker
Volker antwortete auf das Thema: Engine Problem

rsadut schrieb: Hi Norbert,
I am also a member of the 107 SL club. I have access to the EPC. I can check If my engine type has the Hydrostössel.
MfG aus Istanbul
Juan

Hallo Juan.

your car has no Hydrostößel. that only came 1975 with KA-Jetronic.

Viele Schraubergrüße - best regards, Dr-DJet Volker

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18 Jul 2017 00:32 #7855 von Adimechanic
Adimechanic antwortete auf das Thema: Engine Problem
Hello.

I would also agree that it is a sparking problem, maybe with the rotor inside the zundverteilerkapp, as some cars were with limited engine revolutions. That rev limiter, is actuated by the centrifugal force of a smalll weight against a resort( small spring) in the rotor. With time, that device dont work very good. and is messing up ignition times.
As Volker sugested above, is unburned fuel in the exaust. If the engine, idles well, performs well, and is going ok untilll a certain revolution level...it means, that has gasoline, compression and spark. The only one of them that can vary is the spark /ignition advance. Maybe your advance is too high,you can check this on the foot of distributor.
Check also what spark plugs are installed in the engine. Too cold, or too hot. What colour are they?

There are also other things to check, but these are the first ones to look.

Thank you

Adi .
Anhang:

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18 Jul 2017 02:07 #7856 von nordfisch
nordfisch antwortete auf das Thema: Engine Problem
Hi Adi,
Welcome to the forum - you introduced a good new idea. Maybe you are right.

It's great others think about the same item with a different view and another background - I by myself didn't consider the rotor because I didn't have to do with these since - yes, 35 years.

Regards
Norbert

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18 Jul 2017 09:39 #7857 von Volker
Volker antwortete auf das Thema: Engine Problem
Hi,

a wrong working limiter in distribution finger normally means that you come to a certain rpm and then it will not accelerate further. But Adi is right that a loose rpm limiter could create strange effects. Easy to verify though: Use the finger without limiter as listed in appendix A for early M116 engines.

Viele Schraubergrüße - best regards, Dr-DJet Volker

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18 Jul 2017 12:10 #7858 von Adimechanic
Adimechanic antwortete auf das Thema: Engine Problem
Thank you Norbert,

I myself i was a bit "shy" when i first got my 450 SE D jet, but i got over it, and i started to learn how it works.
Also, i am a mechanic for about 20 years, so that helped a bit.

About considering camshaft wear.. i would not discard for completely, because Juan ( Ola Juan :) didnt mention how many kilometers the car has. But, knowing Daimler Benz way of doing things, at leas back in the day : 1. Camshafts are forged, wich is a pretty tough process. 2. M116 and M117 were built to last for a lifespan of 4 milion kilometers.No one did 4 milion kilometers with an engine of this type. At least, not that i know of..

Gruss

Adi

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18 Jul 2017 12:15 #7859 von Adimechanic
Adimechanic antwortete auf das Thema: Engine Problem
Exactly what i was thinking and suggesting in here.

Another posibility, is that some" criminal hand" got to mess up with the rotor. Maybe prevoius owner.., mechanic.. As it did happend to my rotor, in my motor!.. :(



Adi

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21 Aug 2017 23:55 #7993 von rsadut
rsadut antwortete auf das Thema: Engine Problem-ECU
Dear All,

Since the only part in my engine control that I did not change is the ECU I decided to check this part as well.
I attached the picture of the bottom of one of the boards. Since the size of the picture allowed is relatively small the picture quality is not good. However the brown spots are visible. I have cleaned one of the boards. I want to check the bottom board as well but I wanted to get your advice before continuing further. Do I have to unsolder the soldered cables to detach the bottom board?(presented in red semi circles-bottom board jpg )

rgds
juan

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22 Aug 2017 00:14 #7994 von Volker
Volker antwortete auf das Thema: Engine Problem-ECU
Hi,

it is correct that you have to remove all connections to resistors (which you marked red) plus the one to 4 power transistors and power diode befor you can remove lower board.

However I do not recommend you to do so.

Viele Schraubergrüße - best regards, Dr-DJet Volker

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22 Aug 2017 18:40 #7997 von rsadut
rsadut antwortete auf das Thema: Engine Problem-ECU
Hi Volker,

I am not planning to repair the ECU myself.
As you may remember I have this engine problem which loses rpm on a specific throttle level and I have to push harder to accelerate and keep the engine rpm steady.
Members in the forum have already recommended checking the rpm limiter, camshaft wear. My mechanic is suspecting the injectors. I had them cleaned. During this process I have found out that four out of 8 are either performing under and over the limits. The rest are fine. I have obtained five new injectors from my spare part dealer which I keep aside for the moment. My mechanic also recommended to inspect the gas tank as he found some debris in the fuel line? ( I cannot understand this as the fuel filter was recently changed and I have driven the car only couple of hundred kms as the performance is lagging)
My mechanic also checked the engine with another ecu from 3,5 V8 and did not see any change in performance.
However I wanted to make sure that ECU is o.k., too since it is the only part that was not inspected.
It may not be visible in the images due to low resolution but the board was oxidized.
I suspect that the same is valid for the second board.
I am planning to examine the bottom board with an endoscope camera before I attempt something like this.
I read your articles about the ECU and fine tuning after repair.
However I am also helpless.
Can you recommend anyone who is specialized such repairs.
regards
juan

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22 Aug 2017 19:10 #7998 von Volker
Volker antwortete auf das Thema: Engine Problem
Hi Juan,

I do not know anyone in Turkey who could do such a repair. And customs from TR to DE and also back is a nightmare. Otherwise I would offer my help. Maybe you ask Bosch in Turkey if they can help.

I do ot believe in an ECU fault if you have already replaced it once. If your PCB boards are covered from water with a crust, then I can also give you no hope that it can be cleaned. I tried that once and that ECU continued to drift in ints values all the time, no matter how much I tried to clean it. In such a case I recommend replacing it.

Viele Schraubergrüße - best regards, Dr-DJet Volker

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22 Aug 2017 21:56 #7999 von rsadut
rsadut antwortete auf das Thema: Engine Problem
LET ME SEE WHAT I CAN DO TO SEND IT BY COURIER SERVICE TOMORROW.
I HAD SENT MY MPS TO BOSCH (PARTBOB FOR CLASSICS) BEFORE FOR REPAIR.I DID NOT FACE ANY PROBLEMS.
SENDING SOMETHING FOR REPAIR IS NOT A PROBLEM AS LONG AS YOU DO NOT DECLARE A CUSTOMS VALUE FOR THE REPAIRED ITEM.
I CAN SEND TO YOU THE PICTURES OF THE BOARDS IN HIGH RESOLUTION (TOP AND BOTTOM) IF YOU CAN SHARE YOUR E-MAIL ADDRESS WITH ME.
I DO NOT SEE ANY VISUAL DEFECTS ON THE TOP PARTS.
RGDS
JUAN

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23 Aug 2017 10:02 #8000 von Volker
Volker antwortete auf das Thema: Engine Problem
Hi Juan,

well I do not know how Bosch handles this. But the few cases that I have ordered something from abroad have made me end up in customs where I had to proof the value of the goods via the original bank transfer slip or Paypal slip. They would not trust what was declared on the package. And I also remember that customs into Turkey was also not easy.

But maybe you contact Bosch Electronic Service in Germany.

Viele Schraubergrüße - best regards, Dr-DJet Volker

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