400E low idle/stalling especially when cold

[400Erik]

Hi guys,

I recently experienced some problems with my 93‘ Euro Spec 400E when starting it in the morning. When it’s cold it either jumps directly to 700rpm with the ASR light coming on directly, or it stalls and after it had like 3-4 starts it establishes idle below 500rpm close before cutting out for like 10 seconds, until the ECU recognises it, the rpm will go to 700rpm and the asr light coming on. It doesn’t seem like the car is in limp mode (still accelerates properly, reaches topspeed etc., but I can only use the manual range of the ETA).

If I drive the car until it has reached operating temperature turn it of and let it sit for a 15-20 minutes, everything is working as it should. If I don’t wait and try to start it directly, it will hold idle just low enough that it doesn’t stall, until the ECU brings the idle to 1200rpm and the ASR light comes on. Sometimes the ASR light does come back on while driving and the electronic range of the ETA is disabled - but that’s completely random. Sometimes after pressing the pedal just before kickdown in S mode, sometimes while cruising with a constant throttle setting.

On my last trip (600km each), it occurred on the last 20 kilometres after changing Autobahns and on the way back it happened every 30 minutes or so . Pulling codes isn’t helpful (I use carsoft) since there aren’t any, and if I try to read codes while the ASR lamp is on, it’s always something different - mostly fuel related, the last time it said that the coolant sensor was broken, which is brand new). Those codes also vanish when turning of the engine in putting it into ignition only.

Can it be that my fuel pumps are just bad? But why is it then able to idle at a higher rpm/ run normally once its warmed up?

What I’ve replaced so far are:

• Spark Plugs,
• Caps and Rotors (all the correct ones from Bosch),
• Spark Cables (Beru)
• Coolant Sensor,
• O2 Sensor,
• MAF (Brand new Bosch Unit),
• Fuel regulator unit (also Bosch),
• upper wiring harness (new Mercedes Part),
• several vacuum hoses that seemed to be bad, except the one that runs to the ETA, because I can’t get to it without removing the ETA.

I really hope you guys might have that hint I need, so I don’t have to worry about cold starts anymore^^

Greetings from Germany
Erik

 

[gsxr]

Sounds like you have issues with the ETA failing. If it's original from 1993, it's probably overdue to be sent out for a rebuild.

The symptoms you describe will NOT be cured with new fuel pumps.

Carsoft is useless for checking fault codes. Use an analog hand-held blink code reader, click here for details. Better yet, invest in an SDS setup with HHT-Win (and, a fully populated 38-pin data cable). Search the forum for details on the SDS options. Specifically, check for codes on pin 7 (E-GAS module). Clear codes then check which fault codes return quickly.

Welcome to the forum!

 

[400Erik]

Thanks for your help. The Carsoft HHT actually shows the correct codes (according to the Diagram on the WIS) and I can enter BM, LH and ABS/ASR module with it, but maybe it can’t show me everything. Before that I used HFMscan to have at least a look at the LH module, but I couldn’t use it while the Engine was running. Finding the original HHT „Gameboy“ is almost impossible, and if, they’re really expensive. But I will try to blink the codes and see if it does show something new.

Reagarding the ETA: I think it was already redone by someone in the past, because the cable looked quite new (compared to the crunchy Wiring harness I replaced), but I have to check that with the maintenance bills when I’m back home. But wouldn’t a broken ETA cable cause limp mode with reduced power, speed etc.? And how can it then run kinda normal when warm (if the insulation is broken, the cables inside the harness shoud have better contact when warm, causing the ETA to throw codes like crazy?). Furthermore the ETA seems to be active when setting ignition (clicks for 2 seconds, then you can hear it humming). My thoughts are that there is maybe one component that makes it impossible for the ETA to hold idle, so it just turns of the electrical regulation and runs with fixed values instead…

 

[gsxr]

The pre-facelift ETA's typically had good wiring in the external cable, it probably has not been replaced. However the internal components are what start to fail... potentiometers, microswitches, clutch coil, etc. The symptoms usually start out random and intermittent, and gradually become worse / more frequent.

Blink codes will get you 95% of what you need to know. Only the E-GAS module has digital codes which require a digital scanner, as explained in the thread linked above. The original HHT is almost impossible to find (and expensive), but SDS C4 or M6 has HHT-Win support which is an HHT emulator that provides 100% of original HHT functionality - including live data from all modules. See the video below for a sample of what's available.

 

[emerydc8]

Take the air cleaner housing off and idle the engine. See if there are any changes when you disturb the ETA cable. I had a pancake-style connector on my 92 400E and it was trashed. I noticed by accident as the key was on but the engine was not running. When I leaned on the filter housing it would cause the ETA motor to activate. It was a bad ETA cable.

 

[400Erik]

After laying sick in bed, I’ve finally had the time to check what you’ve guys told me to do. I can definitely tell that the wiring (at least the visible part) doesn’t cause the issue. I’ve tried to bend the cable at various points while the engine was idling, but that didn’t trigger any faults. So I guess the internals are bad (as @gsxr suggested) Is it right that the ETA with the old round connector is listed as A0001417925? Unfortunately even Mercedes Classic isn’t able to get me new one, so I’m looking for a used one right now, that I can send in for overhaul. If anyone, preferably from Germany/Europe, has a spare one (ideally one that’s already rebuilt) and is willing to sell it - just contact me.