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Discussion Starter #1
Hi all,

I've been a long time lurker, and bought a 190e back in June, since then I've been working on getting the car to a point where I can drive it daily, I hope at least.

I've replaced a couple of parts, including the radiator switch and idle air control valve.

I suspect this issue is related to the Idle air control valve, as I had to remove the EHA to get to it. Prior to changing this it started and ran fine (besides from an erratic idle which I presume is due to my thermo vacuum valve having snapped off).

So just to clarify the main issue, is that the car will start, but only when I apply gas, and once started, the revs will drop and the car eventually stall unless I press the gas to keep the revs up.

The old idle air control valve resulted in the idle hunting while warm and on the move.

Do we think I have bought a dodgy idle air control valve, or have I done goofed when I removed the EHA?

Are we familiar with these symptoms at all?

In the morning I will try out the old Idle air control valve again just to eliminate all possibilities.

Thanks in advance :)
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,500 Posts
Welcome to the forum. Please state your model, year and mileage so we can all help you in a better fashion,

As you already may know the EHA and IACV are actuators in the system and generally do as they are told.
Every now end then, they may act up but very rarely (particularly the EHA). And in those instances the behavior is bi-modal, meaning they work some of the time and at other times, they may get stuck (due to dirt and grime)

Usually the problem lies elsewhere in the sensors and controllers.
But having said that, there are exceptions of course.

So hopefully you are all set with a Multimeter and are willing to measure voltages and currents in the system.
 

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Discussion Starter #3
Hey Dolucasi,

Thanks for your reply.

It's a 1991 w201 190e at around 120k miles.

I do have a couple of multimeters ready to go, but I'm not entirely sure where to start, and what voltages to expect from those places. (I'm new to w201s).

I do really hope it is as simple as a controller, but the fact that the car was working fine prior to me changing the Idle Air control valve leads me to believe that they are the culprit.

It is also worth mentioning that the idle air control valve is a previously used unit, apparently in working condition, but I got it for cheap and thought I could cross off one of the countless issues with the car.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,500 Posts
And the engine is a 2.3 8V or a 2.6 12V? Sounds like a 2.3L 8V since the 2.6L engines have the EHA and IACV pretty far apart.

Do you have access to a variable (0-12V DC) power supply?

The IACV that was hunting (the original) was probably fine. The fact that it was hunting is a good sign that the ECU was telling it to "hunt". So if you choose to put that one back on, using thin wires, see if you can connect to it's terminals while it is still plugged in and measure the "DC" voltage on it and report on that.

If you decide to chase down what is the state of affairs with the current one you have, unplug the connector and see if there is any difference. The expected behavior is that the idle RPM's will settle at ~1000-1500rpm.
 

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Discussion Starter #6
Hi again guys,

Apologies for the delay in me getting back to you.

I got back to the car yesterday, to see if I can get any information on what's going on, but it started perfectly fine, and has even been idling quite well (albeit quite low, just over 500rpm).

The car is a 2.0 auto, and I now have another problem, and another question, I am hearing a cricket type sound from the back left/centre of the engine bay, (passenger side in murica I believe). I heard mention of a belt tensioning damper (or something along those lines) which I plan on taking a look at tonight. (it gets dark here quickly atm so I'm struggling to find time to get this sorted).

I have taken a look through the merc manuals for my car, but can't find anything about the thermo-vacuum valve? What is it's function, and is me having it disconnected while the car is started causing severe damage?

Thanks for your help guys, I probably should have asked sooner when I was encountering all those other problems 😅
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,500 Posts
The thermo-vaccuum valve turns on (or was it off?) the ignition timing adjustment, which is why it is connected to the ignition control unit (AKA EZL)
I do not believe it will cause harm to the EZL if disconnected, but if you do not plug it it will be a source of a vacuum leak (may not be detrimental to a carb car, I do not know)
 

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I was having trouble with starting and I found that, in addition to crumbling of connectors and hose, that the serpentine belt needed to be replaced. If you have no data on the age of the belt, then this might be a culprit. It will affect electrical, too.

Chatlane
 
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