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I don’t have any technical data about these coils at hand right now. … I would for instance check for resistance differences between cold and hot condition.
 

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Discussion Starter #62

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I stick to the information about resistance differences between cold and hot condition. Maybe you can pull the coils out and take them to someone who has proper equipment to test them.
 

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Just in order not to confuse anybody:
In post # 55 I said: “Even with the problem you describe occuring intermittently …”
Sorry … that was not precise!
I should have said: “Even with the problem you describe occuring at operating temperature …”

Intermittant occurance of the problem would reduce the suspicion on the coils.
 

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IMHO, coil-overs are a consumable item that need to be replaced every so many miles, just like old school distributor and spark plug wires, and they certainly can fail in such a manner that they become heat sensitive.
 

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Yes! … IMHO too they are a strong suspect here.
I just hesitate to let someone, who has already put a serious strain on his budget, go and buy more parts without verification that the old ones are really bad.
 

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Discussion Starter #67
ok read DTC codes using a blink code reader and this is what i got:

4 , 25 , 26

I know:
1.MAF has been disconnected while car was running (has been plugged back in)
2.CMP sensor is broken from its "cover" can be pulled off by hand, its broken where connection meets the roung part of sensor, hard to explain how just by texting, i will post a pic later.

Code meaning:
4 Hot film MAF sensor (B2/5) air flow implausibly high
4 Hot film MAF sensor (B2/5) open circuit

25 CMP sensor (L5/1) not recognized/implausible (segment control)

26 Not used
26 Not used

is what i concluded true ? Also i didn't get what "CMP sensor (L5/1) not recognized/implausible (segment control)" means, and why 26 is not used ? maybe i counted wrong ?
 

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disconnecting the hot wire (LH) MAF used on my volvos when the engine is running is known to be potentially fatal to them and/or the ECU, but I have no idea about the mercedes HFM implementation. I always shut things off before plugging/unplugging anything.

flakey wiring at the CMP could certainly cause problems.


these codes you're getting, you've reset them and they come back after driving ?
 

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Discussion Starter #70 (Edited)
disconnecting the hot wire (LH) MAF used on my volvos when the engine is running is known to be potentially fatal to them and/or the ECU, but I have no idea about the mercedes HFM implementation. I always shut things off before plugging/unplugging anything.

flakey wiring at the CMP could certainly cause problems.


these codes you're getting, you've reset them and they come back after driving ?
Regarding the MAF I assume the code came because of unplugging it while engine was running.

Regarding the CMP, I tried to run the car without CMP and it ran as it ran with the CMP. Isn't that weird ?

These codes is what I got after unplugging the sensor above, I need to delete the codes and do a test drive and then read again, but unfortunately I didn't have enough time today, will do that later as soon as I can.
 

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@speed9644 I recommend getting K-Line interface off ebay and use Mike's HFMScan, it provides digital error codes with correct description with live engine data. I understand it takes time to buy interface on ebay and get it delivered, but looking at date you started this thread it would have taken lot less time.
 

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Discussion Starter #72 (Edited)
After a day driving the car, I feel like there's a relation between brake booster and idle, when car is stopped idle is not smooth and it jerks. Is that possible ? Does the brake booster change vacuum/pressure when brake is fully pressed ?


PS: very interesting thing, the first 10 minutes of driving once throttle body was replaced, car ran like a dream and purred like a kitten with no problem, then it got worse more and more, today it hesitates and jerks and missfires almost every second its on idle.
 

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@speed9644 I recommend getting K-Line interface off ebay and use Mike's HFMScan, it provides digital error codes with correct description with live engine data. I understand it takes time to buy interface on ebay and get it delivered, but looking at date you started this thread it would have taken lot less time.
+1 get the car on HFM Scan it will tell you all you need to know and enable correct diagnosis.
 

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After a day driving the car, I feel like there's a relation between brake booster and idle, when car is stopped idle is not smooth and it jerks. Is that possible ? Does the brake booster change vacuum/pressure when brake is fully pressed ?
If it did and there was vacuum leak you should have seen code 13.
 

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Does the brake booster change vacuum/pressure when brake is fully pressed ?
That’s attentive observing!

Vacuum leaks / false air are fundamental suspects in case of bad idle – and if the leak is small enough, it might only occur at operating temperature.

Like anything connected to the vacuum system in principle, the brake booster can have an effect on it.
Besides the moment during which the booster diaphragm is being moved – there could be a crack in it which changes its shape depending on its brake or not brake position.

Do you see an effect when you apply or release the brake or also when you hold it?

Anyway, a brake booster’s involvement could be tested by disconnecting and blocking its vacuum line.
Of course: Don’t drive like that … do that test w/o moving the car!

IMHO the best way to check the intake system in general for false air is using a smoke machine.
 

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Discussion Starter #76
+1 get the car on HFM Scan it will tell you all you need to know and enable correct diagnosis.
I have bought an OBD plug in and an ELM327 module, but nothing from mike, eventually it didn't work because module couldn't communicate with the car.



If it did and there was vacuum leak you should have seen code 13.
Ok, I did a quick test yesterday, didn't erase any codes before reading codes, I might erase the codes tonight, go for a test drive and then read codes again and report back.


That’s attentive observing!

Vacuum leaks / false air are fundamental suspects in case of bad idle – and if the leak is small enough, it might only occur at operating temperature.

Like anything connected to the vacuum system in principle, the brake booster can have an effect on it.
Besides the moment during which the booster diaphragm is being moved – there could be a crack in it which changes its shape depending on its brake or not brake position.

Do you see an effect when you apply or release the brake or also when you hold it?

Anyway, a brake booster’s involvement could be tested by disconnecting and blocking its vacuum line.
Of course: Don’t drive like that … do that test w/o moving the car!

IMHO the best way to check the intake system in general for false air is using a smoke machine.
But weird thing is that failure of brake booster is not common W124's, I will just try to spray a carburetor cleaner spray near the vacuum lines while my assistance is watching the RPG gauge and see if it goes up/down when spraying. That's just an easier test for me because I don't have enough time to leave work and go search for a shop that can make a smoke test.

Mechanics here are being lasy and don't want to deal with these old cars that doesn't have an OBD2 port, arghh.
 

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Discussion Starter #78
PROBLEM SOLVED !!!



Problem was an ignition coil, it was very intermit, when engine was cold, it ran better, as temp rises ignition coil performed worse probably because the copper solenoid heats up thus resitance increase which lead to no spark.

Car has 270,000km don't know whem coils were replaced, but now I know that coils can make this kind of problems, jerking and random misfires, but misfires occured when car was stopped but its on Drive.

Next step is oil change and power steering oil + filter replacement, probably tomorrow :D

Thanks guys for all your help, you have tought me a lot !!!
 
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