I have been fighting a strange "limp home" problem on my '93 300CE (124.052) for over two years. Every morning the car goes into limp home after 1000'. There is no dash light. I restart the car and it never happens again until the next day unless it is cold and it might take two different failures for it to clear. We have replaced everything on the car except the license plate to no avail. I have gotten many suggestions from you the forum members but the fix has alluded us. From the git go, MB Doc said it was an electrical problem which we agree.
I bought a copy of Alldata for this car. There is a micro switch on the pedal linkage under the dash. When we found this our hopes raised and we replaced it. No help. However in reading about this switch in Alldata the following statements were made: "The safety switch for the acceleration pedal position sensor then takes over the voltage supply for the fuel pump relay or the engine systems control unit. So that there is no switch gap when the accelerator pedal is moved quickly, a SWITCHING TRANSISTOR takes over for the fuel pump or the engine control unit for a short time. The maximum current flow may not exceed 1 amp. The switching transistor is not protected from short circuits to ground."

Does anyone know about this transistor or where it is located. Do you think it might be inside the Electronic Throttle Actuator? Anybody have any ideas?
Anziani
'93 300CE 202K
'95 E420 122K

Still sounds like a (over) charging issue on that 1st start.

Have you connected a voltmeter & watched the voltage as the problem happens?
Have you ever had a trickle charger on the battery over-night & see if that still happens?

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I'll do some voltage tests over the next few days. We just installed a brand new Interstate 84 month battery. The alternator is about two years old and has had the regulator changed twice.
Thanks for your interest.
Anziani

mb doc,

Are the battery terminals the best place to monitor voltage? If not, where do you suggest?
Anziani

The easiest is at the cigarette lighter.

Connect voltmeter to that type of plug.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Set up a voltage monitoring system and cannot see anything out of whack. With the key on the voltage reads about 12.6 With the engine running I get a steady 14.1-3VDC It has gone into limp home 4 times in 2 days but I only observed one high reading of 14.82
Now my question is: "is 14 too high?"
Anziani

After a week of voltage testing, I can find nothing wrong. The voltage measured from the led counter shows a steady 13.6 to 14.2 VDC. At idle with the lights on it still reads at 13.6. Driving at different speeds changes nothing. I have a VERY stable charging/battery system.
The couple of times that I caught it going into "limp home" I could see no difference although I thought I saw a reading of 14.8 once.
So apparently erratic voltages are NOT the source of my strange problem.
You guys are welcome to jump right in with suggestions.
Anziani