16-Valve idle no one can figure out
 

I have a US model '86 190E 16-Valve.

The card idles at at least 1300 RPM. I've taken the car two two M-B dealerships and four independent shops and no one can find the problem. The car idles at about 900-1000 RPM when cold, but as soon as the engine warms the idle shoots up. The idle is not really erratic, but it's a little hard to say before because of the impact of the AC engaging. Here is list of what has been done/checked:

-OVP relay replaced
-Idle control valve replaced
-EZL computer replaced
-O2 sensor replaced (sensor good, but no signal at sensor)
-Intake manifold removed. All boots, gaskets, hoses replaced. No techs can find a vaccum leak
-Cam timing checked
-All temp sensors checked
-Throttle plate adjustment checked
-Fuel/air mixture checked
-Engine wiring harness checked
-Valve clearance checked

After swapping out the computer, shops either indicated the harness must be bad (despite the fact that no one has found an issue with the harness, or that the already replaced EZL computer (this was actually replaced twice) or that the idle control valve must be bad).

FYI - One shop indicated cutting off the air flow to the idle control valve produces perfect idle.

I must note that my ignition switch has a problem (I had the same thing with another 190), to engage the AC and blower motor I need to turn the key back a tad. Could this have anything to do with the high idle?

Any help would be appreciated. I have spent an incredible sum of money trying to fix this problem. Everyone says they can fix it, and they can't.

That is a COMMON 16V problem! 99% of the time the problem is the air flow position sensor! Have replaced at least 20 of them for that exact problem.

MB part number 000-074-23-14(complete housing w/sensor) with a list $675! takes 2.5-3 hrs& requires several other parts

I'd have to agree with DOC. If you would like to be certain that it is the sensor conduct the following tests.

Disconnect the sensor and measure the three wires for voltage, one wire will have roughly 5V. This is the reference voltage to the sensor. Measure the two remaining wires for a Ground circuit. The third wire is the air flow position signal, the feedback voltage to the control unit.

Now that you have an idea of the three wires and their purpose reconnect the sensor but leave the pins somewhat exposed so they can be probed with meter leads. With the engine running measure the feedback voltage signal, specification is approximately .5 V to .9 V.

Happy motoring to you

This solved my idle issues.
http://www.peachparts.com/shopforum/tech-help/116273-figured-out-16v-idle-problem.html

16-Valve Idle Problem
 

You guys offered me some promising advice regarding my 190E 16-Valve's idle problem that no one can figure out. With both of you suggesting the air flow position sensor. I looked back at my records and one of the shops did break things down to the throttle body, to check some things including the air flow sensor. Anyway, Doc, I live in Atlanta and would like to bring the car to you if possible for diagnosis. Let me know where to find you.

Sincerely,

Kurt

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[M.B.DOC]That is a COMMON 16V problem! 99% of the time the problem is the air flow position sensor! Have replaced at least 20 of them for that exact problem.

MB part number 000-074-23-14(complete housing w/sensor) with a list $675! takes 2.5-3 hrs& requires several other parts[/QUOTE]

[MrCjames]
I'd have to agree with DOC. If you would like to be certain that it is the sensor conduct the following tests.

Disconnect the sensor and measure the three wires for voltage, one wire will have roughly 5V. This is the reference voltage to the sensor. Measure the two remaining wires for a Ground circuit. The third wire is the air flow position signal, the feedback voltage to the control unit.

Now that you have an idea of the three wires and their purpose reconnect the sensor but leave the pins somewhat exposed so they can be probed with meter leads. With the engine running measure the feedback voltage signal, specification is approximately .5 V to .9 V.

Happy motoring to you