So here's my story.
I have read quite a bit of what can cause my 300te to run perfectly from zero cold to Idle warm up.

-Warm up happens at about 20min and 80 or so degrees.
-Once that warm up happens:

Idle begins to sputter
fuel economy gauge shows deteriorating economy settings
Revs start to fluctuate from 700 down

withing a few minutes more- gets worse and eventually dies. refuses to start.

I let it cool down, bingo -like nothing. until it comes to full running temperature...again.

I've replaced Oxy Sensor, plugs, wires, rotor, cap, coolant temp sensor.

Last night, I followed advice and disconnected the connection shown in the red box- was told this eliminate the automatic fuel injection management.

Still had the same exact problem?

Have the feeling the problem is at my fuel distributor, ICV or Mass Air Sensor.

Any thoughts would be appreciated. I have both the Haynes and E-Class Bible but I don't see anything specific to what's happening to my 300te.

Regards

Let me clarify. My ICV is in place when I do this test of unplugging whatever that is in the red box. sorry.

Possibly bad temperature sensor for the fuel injection. (Big black plug) Or bad air meter potentiometer, which is the thing in your pic. It can be finicky to replace....a bouncing idle usually means that it is worn and not giving proper signal to the computer anymore.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I replaced the coolant sensor that shoots info. to the fuel injecting system. On top of the block all the way to the back near the firewall. Today I notice cracks on both lips of the hoses that go into the ICV- I heard it's a pain to change them, but I guess I will. I'm worried you are right and it's the air potentiometer. Will try to find some info on replacing/adjusting that.

This seems to be a growing problem for cars of your (and my) age, or maybe it's just the M103 motor. I've been chasing the same symptoms for several months. The thing that's made the greatest difference so far for me is replacement of the throttle micro switch. It's a little white/gray plastic component in the middle of the throttle linkages behind the fuel distributor. I've also replaced the ICV and the 4-pole temp sensor, but the micro switch was the key so far. It's not back to 100% yet, but much better; no more low rpm stalls at operating temp. Inexpensive part, easy to install.

Now the vacuum hoses from the ICV, that's a different story. I don't know how those get replaced; there's no room to reach a hand under there to connect the new hoses to their ports. Is it necessary to remove other things (like fuel pressure regulator) to gain access? I cannot find the writeup for replacement of these hoses in the FSM. Maybe someone who's done this can chime in.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Ignition coil! These are classic symptoms.

__________________
600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.

I see. I will look for that switch behind the fuel distributor. I have noticed that almost every switch/connector benefits from cleaning but I haven't looked at that switch.

I found an article on replacing the ICV hoses but I will to find it tonight- have it at home and post it here. Has pictures but it doesn't look like a 5 minute job.

Had not thought about the coil. Would think that is mainly an initial start unit and since the car runs perfect during warm up- didn't cross but I will check it. Sounds like I should invest in a new coil anyway. It does look a bit on the worn side- I have 225K. The Oxy sensor I took out looked original so might as well with it some newer blood.

thx for the advice thus far.

I found the link with the images for the ICV hose replacement. It is from one of the other site forums so I hope it's ok to post it here..It has great pictures of the process..

Replaced Hoses on Idle Speed Air Valve (ICV) - Benzworld.org - Mercedes-Benz Discussion Forum


With my wagon, I disconnected the power to the power to the ICV and the car still warmed up to idle (80degrees) and died.

I figured out how to use the built in diagnostic light and it gave me code 4
.. Poetentiometer current illogical

Does anyone know what it all means? strictly wrong voltage to the air potentiometer?

I'm working on getting the coil replaced.

I cleared my codes (reset) and no longer get the error code for the air potentiometer.

What I did yesterday is adjust 1/8 - 1/4 either way and it was made worse so that tower adjustment seems to be optiomal.
Is there any other adjustment that I can do---only for the idle stage? once the system if fully warm at running/idle temperature?

On mine when it started having issues I replaced:

-Wires
-Spark plugs
-Rotor
-Cap
-Coil
-ICV
-Air Pot sensor
-Injection temp sensor
-Air intake sensor (yours being an 88 does not have this)
-EHA valve (it was leaking too)
-Made tiny adjustment to fuel mixture to richen it
-Air filter
-Fuel filter
-OVP relay

Tested micro switch on throttle to be working properly otherwise I'd have done that too.

Ever since its been running great!

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Yes.That's exactly what I might need to do. Someone suggested I disconnect the EHA- so I did that.
No difference. Got warmed up in 15min or so. fuel economy gauge pummets, idle surges and misses, until it dies.

1/2 hour later, start it and it runs perfect. I mean perfect. I'm starting to lean to the fuel distributor? or air potentiometer? thx for the imput and will continue to upgrade parts.

Also: oxygen sensor plays a role in running quality beyond warm up cycle too.

What is likely happening is that the warm temps are causing something to ever so slightly go out of whack (like the air meter sensor) and once warm its not giving proper feedback thus causing the poor operation.

What codes are being thrown when this happens?

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I'm getting 9 blinks of the red diagnostic led. I went to look at the connectors on the main engine harness and found brittle parts. One in particular (the first valve/sensor near the middle of the engine block up top. I believe that is a temperature sensor for the AC---located to the left of the fuel distributor.

That plugs is done with. Here's a picture.

When I look at code 9 it tells me it 'circuit 50'?

thanks again.

You have the red LED, so yours is a California version car? If you're reading 9 flashes, that decodes to the "electric actuator," the EHA valve. That code would have been set when you disconnected the EHA for testing it. Be sure to clear the code after re-connecting the EHA, and see if that 9-flash code returns after driving a while. The 2-pole sensor in your photo is a coolant temp sensor that activates the high speed auxiliary fan when engine temps reach about 105 degrees C.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

OK. Thanks for the help.

I will be looking at a wagon an 1hr away tomorrow saturday. If I don't go with that, I might take your parts.
For now,

Could you give me an idea of total , including shipping for the following:

-complete fuel distro- i'm looking for a complete unit (to avoid adjusting eha/air potentiometer.)
-ICV
-Coil

thanks again. Miss my wagon and how it drives when I"m able to do that more than 20min at a time.