Mercedes-Benz Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
2,446 Posts
Discussion Starter #1
Hi all, I have a w126 300SE, but I like to come here with my engine problems because the 300E folks seem to have most of them. The 126 forum is more geared toward V8s.


I have a problem that's been getting progressively worse. My engine seems to randomly lose power, or won't gain until it's been running awhile.

First thing in the morning when its' cold, it usually runs well. It also loves cold weather.

When I start it up and take off, the engine has no power at all unless I let it run for a long time. Cold or Hot really doesn't matter. If I shut it off for a period of time, then start it and try to leave, I have all I can do to get to 40mph, and 55 is out of the question. Then it will gain in power and run just fine. Most of the time, it runs extremely well.

Basically, until it's been running a bit, it acts like a cold carburetor with a stuck choke, bogging down and barely wanting to move.

I checked fuel pressure many times, and it has been fine. The plugs, wires, cap and rotor are fairly new. The cylinder head was rebuilt and a new gasket installed about 30K miles ago now, the car currently has 208K miles on it.
 

·
Banned
Joined
·
7,361 Posts
I checked fuel pressure many times, and it has been fine. The plugs, wires, cap and rotor are fairly new. The cylinder head was rebuilt and a new gasket installed about 30K miles ago now, the car currently has 208K miles on it.
Have you checked the differential pressure between upper & lower chambers?

Should be 0.5 bar difference, check for voltage at the EHA. I think it's 450ma
but I would have to check WIS on that.

What's you lambda at, is it oscillating or fixed?
 

·
Banned
Joined
·
7,361 Posts
What does the EHA do ? I have a 300se also with 3.0 motor,and its leaking gas there.
The EHA controls the pressure between the upper & lower chambers of
the fuel distributer, making it harder or easier for the air flow plate to
move down which controls how fast and how much fuel gets to the injectors.

On the older CIS cars this was controlled by a mechanical warm-up regulator
with electric assist and vacumn inputs.
 

·
Registered
Joined
·
2,446 Posts
Discussion Starter #5
The duty cycles are fine. No leaks at the EHA. That's what's so strange. Once it warms up and runs well, it runs REALLY well. This is something that only really occurs after the car is first started for maybe the first 5 minutes of operation. Cold or hot doesn't matter, but it bothers worse when it's warm. about 80% of the time I fire it up in the morning and it runs well cold.
 

·
Registered
Joined
·
8,119 Posts
The EHA controls the pressure between the upper & lower chambers of
the fuel distributer, making it harder or easier for the air flow plate to
move down which controls how fast and how much fuel gets to the injectors.

On the older CIS cars this was controlled by a mechanical warm-up regulator
with electric assist and vacumn inputs.
would a leaky EHA cause a stumble on cold start up? I just got a used one one ebay 78 bucks ,looks decent,waiting on o rings to arrive.
 

·
Banned
Joined
·
7,361 Posts
The duty cycles are fine. No leaks at the EHA. That's what's so strange. Once it warms up and runs well, it runs REALLY well. This is something that only really occurs after the car is first started for maybe the first 5 minutes of operation. Cold or hot doesn't matter, but it bothers worse when it's warm. about 80% of the time I fire it up in the morning and it runs well cold.

Coolant temp sender, very sensitive on these, check that.
 

·
Registered
Joined
·
2,446 Posts
Discussion Starter #9
Coolant temp sender, very sensitive on these, check that.
A HA! That is something I have not checked. Will do so tomorrow. Does anyone have the specs off hand? I'm too full from dinner to get up and go get the CD manual set :)

Happy Thanksgiving to all!:)
 

·
Registered
Joined
·
2,446 Posts
Discussion Starter #10
would a leaky EHA cause a stumble on cold start up? I just got a used one one ebay 78 bucks ,looks decent,waiting on o rings to arrive.
:( you probably just needed to replace the tiny O-rings that seal the EHA to the FD. I have tried this before. You never know if the replacement has been monkeyed with or adjusted- best to use the one that belongs to the car if it was running well before it leaked. If the valve is leaking internally or is cracked, then you would most certainly need to replace it.
 

·
Premium Member
Joined
·
6,734 Posts
:( you probably just needed to replace the tiny O-rings that seal the EHA to the FD. I have tried this before. You never know if the replacement has been monkeyed with or adjusted- best to use the one that belongs to the car if it was running well before it leaked. If the valve is leaking internally or is cracked, then you would most certainly need to replace it.
and use the correct replacement o-rings, not generic stuff you get at your friendly neighborhood bigbox chain chrome hubcap -n- wax store...
 

·
Registered
Joined
·
1,128 Posts
I seem to have a similar issue.

Although it happens completely without any apparent conditions.

Engine will rev perfectly in P or N, but once in Gear, sometimes, maybe every 10 drive cycles, the car won't rev past ~2000Rpms, ONLY when in gear. The car will accelerate only if I pump the accelerator.

It feels like it's hitting a governor, no stalling, no rough idle, fuel supply is okay.

It won't suddenly do it either, it either will do it and not kick it, or run perfectly.

ANY ideas?
 
1 - 15 of 15 Posts
Top