M111 cold start issue

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samir96

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Sep 17, 2014
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15
Car
Mercedes - Benz W124 E220 '94
hey guys, i have a W124 E220 '94 , i'm experiencing cold start issues when the engine is cold (first couple of starts at the morning,or fist start in a certain day), it would start at first crank but thats not the problem, the idle is very low and tends to make the engine stall, first second it will go near 1000 RPM and then goes down to 500 and will start to vibrate and stumble and then stall, if i throttle it up to 1500RPM it will raise above that slowly, if i leave the throttle while the engine is still cold, it would go to the lowest RPM and stall.

Here's a cold start video: MOV_0032 (download the file and watch it)
Note: when RPM is steady / above 1000RPM i was throttling.

What i've done:
1.Fuel pump + Fuel injections were replaced, OEM of course.
2.Fuel pump relay (OEM) changed (helped the rough idle a very little bit).
3.Plugs also changed, didn't found Bosch F8DC4, so i went for NGK and Beru.
4.Cleaned throttle body, and MAF sensor.
5.OVP replaced with another one from my Mech.

Things i am concerned about:
1.Is the M111 suffer from brittle wiring insulation, and biodgrable wiring harness, also about the throtle body, the build date is not visible (the stamp is torned) its mostly before 1998.
2.Vacuum leaks, and 20 years old plastic, this may cause vacuum leak, how can i properly check if there's vacuum leaks (smoke test ?)
3. i haven't changed coil packs, and i think that PO didn't do it too ( he has neglected the car, and has made some bad mistakes you don't want to know what he has done (interior not mechanical)).
4. any other things i need to check before i change the damn wiring harness or throttle body ?
 
Listening to the clip sounds to me that you have a misfire which points to a possible coil failure or a failure of the ECU section that triggers the coils. A common problem also on these engines is the wiring to the MAFF because its clipped to the cam cover which cooks it!
 
yeah, my next step is to change both of the coils, and see what happends.
yeah i know about the wiring problems AGH how much i hate that !!!
 
If you can get the engine to run for some time then take out the plugs. The coils fire 1+4 and 2+3 If its a particular coil or ECU power transistor then 2 plugs will be fouled and the other 2 much cleaner in appearance. If its an ecu Power transistor then it can be replaced.
 
grober said:
If you can get the engine to run for some time then take out the plugs. The coils fire 1+4 and 2+3 If its a particular coil or ECU power transistor then 2 plugs will be fouled and the other 2 much cleaner in appearance. If its an ecu Power transistor then it can be replaced.
Click to expand...

but first i need to make sure they are clean right ?
also, I assume, i should try this with the engine cold, that it would misfire. because this doesn't happen with the engine hot.
 
If there is no misfire when the engine is hot then its not likely an ignition problem. Faulty coils/ecu don't usually disappear with a warm engine. Might still be worth pulling the plugs and examining them as they can tell you a lot. The other thing that causes a misfire at low revs/cold is a weak mixture which might again be deduced from the plugs.
 
grober said:
If there is no misfire when the engine is hot then its not likely an ignition problem. Faulty coils/ecu don't usually disappear with a warm engine. Might still be worth pulling the plugs and examining them as they can tell you a lot. The other thing that causes a misfire at low revs/cold is a weak mixture which might again be deduced from the plugs.
Click to expand...

i have changed plugs 3 times, each time with a different plug, however, all of them weren't what the engine is supposed to run with because i couldn't find the right ones (Bosch F8DC4) I tried to call my dealer and ask them if they have but they just tell me we will call you back :mad: and they haven't called me back !!!

how can i adjust/reset mixture in the M111, there's no mechanical , its all electronic...
 
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bump...
any other ideas/suggestions ??
 
Can you get live fuel trim data from the ECU on your car? Shouldn't that tell you if the car has a mixture problem?
 
Grey Area said:
Can you get live fuel trim data from the ECU on your car? Shouldn't that tell you if the car has a mixture problem?
Click to expand...

I don't think ECU has a option to get live fuel time data, its 1994, it has 16-pin, code reading is got by a blink code reader, it doesn't have an OBD2 maybe its OBD1 or not OBD....
I don't think there's a problem in the fuel pressure, due to I have changed the fuel pump and the fuel injectors.
 
I think c classes of a similar age are OBD 1 so I would be surprised if the E class wasn't. Kind of a moot point anyway if you don't think it'll do live data on a STAR.

When you did the fuel pump change did you change all the fuel filters?

Maybe the mix is wrong from the air side of things, if you follow. A bad oxygen sensor could be messing with the air flow to the engine on start up causing a bad mix.

Does anyone know more about the systems in play vis a vis fuel/air mix on start up? I assume there's some routine that acts in a similar capacity to an 'automatic choke'?


Before you do much more, and definitely before you start messing with the wiring looms and ECU, I would recommend a STAR diagnosis for whatever data you can get. If it's a sensor then you could end up throwing a s**t load of parts at it and see no improvement which is very costly. HTH.
 
Have you checked the coolant reservoir for oil scum/staining or the oil for steaks of white emusion. Sometimes a misfire from cold overnight is a sign the head gasket is going. Normally if you look down the plug hole with a torch the top of the piston affected will look black and oily [ its wet not oily] and so will the spark plug. Not saying its that but worth checking.
 
ok so i have pulled off some codes from the ECU, i have made a blink code reader.
errors i got:
pin #7: 34 , 2

now i need to find what does that mean.

PS: will this DTC work ? it doesn't specify the E220.

donno if that works on M111 or not but pin 7 is for Automatic Climate Control, 34 is Auxiliary fan 2nd stage (actuation) short circut i think that means that the High/Low pressure sensor is bad. 2 blinks mean in car tempreature sensor - short circut -> where is this sensor located ?

however, that doesn't help me because im having a cold start issue.
any suggestions ?
 
Last edited:
pin 8 are all the engine codes.

Read those and let us know what comes up.
 
on pin 8 i got a dim 1 blink
 
M111 of 1994 does suffer from harness degradation problems
The 16-pin diagnostics port is OBD1, yes, but live ECU data is also available :) Look for hfmscan (software by a Russian programmer) and an appropriate interface if you want to go that route.
what NGK plugs have you been using? (I'm asking this not because I suspect them, but am also in same dilemma. No F8DC4s in sight, and Mercedes here gave me FR8DC4+, which I'm a bit doubtful of. I think I will end up using them however)
 
sicelo said:
M111 of 1994 does suffer from harness degradation problems
The 16-pin diagnostics port is OBD1, yes, but live ECU data is also available :) Look for hfmscan (software by a Russian programmer) and an appropriate interface if you want to go that route.
what NGK plugs have you been using? (I'm asking this not because I suspect them, but am also in same dilemma. No F8DC4s in sight, and Mercedes here gave me FR8DC4+, which I'm a bit doubtful of. I think I will end up using them however)
Click to expand...

yeah....
sorry, i don't remember which NGK plugs i've used, because now i've changed them to Beru, same symptoms, spark plugs isn't the cause of this symptom.
 
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its not the spark plugs, there's something wrong, donno what and i need some M111 professionals to help me out....
 
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