Hey guys! I have a 1991 Mercedes’ 300E with the m103 engine and a 4 speed automatic transmission with 157k miles on it. Where do I start…the issue’s I have been having with this car won’t go away. Starting out with the idle. Whenever I start it (even if it’s been sitting for 1hr plus) the car fires up then the idles drop to about 4-500RPM. It only stays started on its own when I start it after a night of sitting, when I start the car after about an hour or so it fires up then immediately dies unless I give it throttle. The second issue is once I have let the car warm up fully and drive off there is absolutely zero power, not only that but the transmission seems to not know what to do. It shifts down, then up, so on and so on but then stays in a gear with the RPM’s at about 4000 but still ZERO power. At this point I hear a weird very popping that is coming from the engine/transmission area (still can’t figure out exactly where) eventually after that whole fiasco it starts driving okay but then I come to a stop light on top of it idling low most of the time there is still no power when I step on the gas, even if I floor it until it reaches 3500-4000 RPM. Later on into driving it the car still doesn’t have much power up until it reaches 1500-2000 RPM. ON TOP of all this it shifts into first gear so hard the car and myself jerk. The gear shifting after the car is driving normally (or wha is normal from this car so far hahah) seems to take a long time to down shift.

I am so tired of having these issues and am thinking about selling the vehicle at this point which is the last thing I want to do. I love this car with my whole heart when I’m cruising it’s the smoothest and most perfect ride. I really need help with this I don’t know where else to go. There aren’t any mechanic’s in my area that know how to work on these cars.

here is a list of everything I have done to it. All of this was done within the last 4 months.
new idle control valve and both hoses that connect to it have been replaced as well
new fuel filter
new upgraded OVP relay (2 fuses)
new Bosch spark plugs properly gapped, new ignition wires, new Bosch cap and rotor
new air filter
checked cold start valve, works perfect
replaced some old vacuum lines (still working on replacing a couple more)
replaced all the smaller fuses just incase
cleaned the idle switch at the cable.

I know it’s a lot of information I need help with but this is my last resort, I don’t know what else to do. if you guys have any idea’s that are too detailed to type up private message me and we can chat on the phone.

Thanks in advance!

 

So I checked and fuse #7 and #10 were blown, #10 looks like it melted. Which is weird because they are about 2 months old. I’ve put less than 300 miles since replacing everything I listed.

 

I'm having the exact same symptoms on my m103. Did you get it sorted out? I changed everything you did as well as fuel pumps and injectors.

 

test your eha on the fuel distributor, or replace it

 

No unfortunately I have not been able to fully sort everything out. I’ve been stuck on this issue for what feels like forever. EHA is next lol.

 

Hey! I’m wondering how can I test it?

 

Hey vonkamp after a lot of research and help I figured out the issue was in the EHA located on the back of the KE-Jetronic system. I took the sensor off (came off really easy 2 torx screws) then I went and flipped the EHA around to reveal a flat head screw. I took that off and underneath was the adjustment, a 2 MM Alan key. I turned it very very carefully only a quarter turn. Now keep in mind the adjustment isn’t tightened any movement of the Alan key will result in the screw underneath moving. Turning it clock wise riches the mixture which completely fixed my low idle issues, my transmission shifting issues, the power issue when launching and the hard start issues after the car sits for a couple hours. Turning it counter clockwise will lean it out so be careful how you adjust. Check out this YouTube video it helped me out a ton

 

That's awesome, so glad you got your car running good. I will zero in on the EHA next. Thanks for responding!

 

I'm curious why you guys are not just measuring what the ECU is telling you is wrong with the car? Why not put a voltmeter on the pin 3 to pin 2 at the diagnostic x11 port?
Probably has some valuable information there. That is telling you what is presently wrong, and the other diagnostic port by the battery (I think 16-pin one with the cap for your year model) will have stored emission issues as well.