Linkage could be stiff. Mine looked ok before I removed it and lubricated the joints. It's worth the 30 minutes work before buying more parts.

What did the CEL code indicate?

__________________
'88 300TE, 175k, black RENNTech 3.6L Recaro C's AMG 1 SOLD
'92 500E, 110k, Spruce green, stock SOLD
'94 E320 Cabriolet, 130k, E500 wheels, Emerald green SOLD
'94 E320 Cabriolet, 110k, black, stock, SOLD
'88 300TE, 229k, dark grey, SOLD
'90 300CE, 212k, white, new paint, SOLD
'91 300E, 209k, white, rebuilt head SOLD
'74 914-6, grey, 2.7L 325hp twin turbo Audi conversion

How do you read the codes? I know where the diagnostic plug is and the little button + red LED, but I don't know how to use it.

The linkage seems to move ok, I also added lube when I was working on it.

__________________
-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)

Search engine is your friend, got this from a post:

The engine needs to be off, but the key must be in the "on" position.

Hold down the button for 3 - 4 seconds and count the blinks. The number of blinks is the code. Repeat the process again. If you get the same number of blinks, you have just one code. If you get a different number of blinks, then you have more than one code.

When finished, turn the key off, then back on, and hold down the button for 6-8 seconds. When you start the car back up, the CE light will be off.

The only codes that will cause a check engine light to illuminate are codes relating to smog equipment. Your ECU will hold a lot of codes that will not cause that light to come on.

91-93 190E and 300 series (2.6L and 3.0L)
1 No faults in system.
2 Throttle valve switch(full throttle contact).
3 Coolant temp sensor.
4 Airflow sensor potentiometer.
5 Oxygen sensor.
7 TNA (RPM) signal.
8 Altitude pressure signal from EZL Ignition control unit.
9 Current to Electro-hydraulic actuator.
10 Throttle valve switch(idle contact).
11 Air injection system.
12 Absolute pressure valves from ELZ ignition control unit.
13 Intake air temp signal.
14 Road speed signal at CIS-E control unit.
16 EGR.
17 Oxygen sensor signal.
18 Current to idle speed air valve.
22 Oxygen sensor heating current.
23 Short to positive in regeneration switch over valve circuit.
25 Short to positive in start valve circuit.
26 Short to positive in shift point retard circuit.
27 Data exchange fault between CIS-E control unit and EZL ignition control unit.
28 Loose contact in coolant temp sensor circuit.
29 Difference in coolant temps between CIS-Eunit and EZL unit.
31 Loose contact in intake air temp sensor circuit.
34 Faulty coolant temp sensor signal from EZL unit.

The code will immediately or eventually come back if you don't resolve it.

My linkage looked fine too but complete removal, cleaning, and lubing the pins, joints, and moving parts resolved my idle issues. Merely spraying it with WD40 did not.

__________________
'88 300TE, 175k, black RENNTech 3.6L Recaro C's AMG 1 SOLD
'92 500E, 110k, Spruce green, stock SOLD
'94 E320 Cabriolet, 130k, E500 wheels, Emerald green SOLD
'94 E320 Cabriolet, 110k, black, stock, SOLD
'88 300TE, 229k, dark grey, SOLD
'90 300CE, 212k, white, new paint, SOLD
'91 300E, 209k, white, rebuilt head SOLD
'74 914-6, grey, 2.7L 325hp twin turbo Audi conversion

My car is a 1990, manufactured in Nov 1989....will that make a difference?

I verified that my linkage moves smoothly....and clicks the microswitch properly......so thats probably not the issue.....

Thanks for the code info....I will check that out today....

__________________
-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)

If your idle control valve is anything like the one on my BMW this might work. Remove the valve and spray into it with carb cleaner. mine was stuck in a partially opened position due to gunk. I had to spray it about three times before it loosened up.

Also try putting it back on and then disconnecting the O2 sensor. If the engine runs better, the sensor is shot.

__________________
"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

Current
Monika '74 450 SL
BrownHilda '79 280SL
FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
Krystal 2004 Volvo S60
Gone
'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf ‘86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
'63 Corvair conv
'57 Nomad

I tested the idle valve when I had it off, and it operated properly when I applied 12V to it.....doesn't seem to be stuck, I cleaned it out a few times with carb/throttle cleaner too....

__________________
-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)

the fuel injection and idle the 300E is controlled by the PCM not by a control valve and I can prove that.

To check fuel pressure you need a fuel pressure tester

http://www.sears.com/shc/s/p_10153_12605_00902169000P

Whatever you disconnected to make the problem go away was not the idle control valve since the system doesnt have one. The round part with 2 prongs is the idle speed adjuster.

Also check this:

test coolant temperature sensor
test starting device of KE fuel injection system

I need your email for those docs btw

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

My 300SE had the same exact symptoms after my coolant temp sensor broke. Seriously, the same EXACT symptoms except I never tried disconnecting the idle circuit.

But I would have to hold the gas when starting, make it rev to 2K for a couple minutes, then it ran fine.

Worth a check, very easy to test. I just posted how to test this in another thread.

-tp