Info needed on IAVC

[SuperCow]

I bought an 190E 2.0 automatic from 1985 with some work. (euro model)
It has an IACV (Idle Air Control Valve) with 3 leads (A0001411725)


But its making an buzzing noise when the ignition is on.
When I look in the air tube of the IACV I see the turning valve closing for 5 seconds, then it pulsate open for a small moment and tries to close again and repeat the cycle.

It this normal? I did a little cleaning with breakcleaner, but didn't help.
When the engine is warm the idle is fine, but when cold its rough it doesn't get the higher idle. When I switch into drive the engine can stall.

I i think it has to do with the IACV. But don't know how it operates at normal

Any opinions?

[SuperCow]

Update, i think the IACV is oke.
If i pull the plug with an running engine the rpm goes up with 300 rpm
Also if i bypass pressurevalve from the A/C (empty) the rpm goes a bit up

[Stretch]

If you look in the FSM there's a detailed section on how to test the air idle control valve...

...I've been meaning to do it on my W201 for a while now but I need to make up a test lead so the current can be measured.

I have a bit of an uneven idle that I've been chasing and I'm of the opinion (but a bit stuck trying to check and confirm) that this is due to an uneven voltage going to the air idle control valve. I did change the alternator to a new one so I'm pretty sure that the source of all electrickery is good...

...for some reason or other summit else is disrupting the signal to this valve. I put it down to either the fuel "hydraulic" sensor (can't remember what it is called) or the oxygen sensor causing the grief.

At the moment I can't really help - all I can say is that this CIS system is infuriatingly simple and yet so difficult to diagnose and fix.



######


A pointer for your problem could be

1) The joint temperature sender - this should detect coolant temperatures below 80 degrees C and then tell the computer to bump up the idle.

2) Air / vacuum leaks in the hoses

3) There's some sort of connection between the automatic transmission and the CIS brain I think

[Stretch]

Oh yes - if you want to meet and play about with a digital oscilloscope this might be possible

[SuperCow]

Yes i have the FSM for it
You have a 2 wire iavc, this one does have 3 wires its an older kjet version (2) from 1985/9 its kjet 3 with a 2 wire steppermotor.

The car is from 1985 January, but it does have A/C that why it does have an iavc, otherwise it would have an manual control you could adjust.

But this car is a bit strange, because it does have an cat with lambda control (no aftermarket)
Also it does have the TSZ ignition, not the EZL with the adjusting knob.

The (one) wire tempsensor is fine, the idle mircoswitch works (but does not surge as the FSM suggest, rev up to 2000rpm and press the switch)
The potmeter was way out, 1.4v on idle, should be 0.7v, i adjusted it a bit, but didn't do much, only the rpm stick a bit more when i depress the throttle...

I'll replace the potmeter with an aftermarket soon.

Vacuumleaks could be, i plan to remove the injection system for an close look, i did spray with breakcleaner and didnt notice anything.
And yes the starterlockout from the automatic goes to the kjet ecu, i haven't tested this yet,



Maybe i should place an 15k resistor (-20 degrees) to the tempsensor to see if i get the 1200rpm idle



This car will replace my diesel because of the tax sigh.
But its an projectcar, it got the important options, klima, tempomat, 4 elec. windows, ABS, seat heater, lotsa KM 275.000
For a price i cant even buy an bicycle lol.

An meet could be nice, I can bring my elec. schema's for all w201 models and options, you can copy your 201.018 from it (i have them all from Mercedes on paper vol 5.0 and 5.1)

[Stretch]

Sorry for the delay - a meet would be good. Long over due. Next week is already full => week after?

[SuperCow]

Sure, no problem, distance is oke, 150km

I've tried the 15k resistor instead of the tempsensor ecu, and the motor revs up to about 1200rpm

Maybe the tempsensor is not to good.

[Stretch]

I thought I'd come and see you but if you want to head North that's fine by me.

As for the temperature sensor

Do you have the four or two pin version?

Checking the four pin is easy as you measure the resistance diagonally across the pins - if the measurements are different from corner to corner then you've got a duff one.

If I remember correctly there was a resistance limit / value mentioned in the FSM somewhere for the temp sensor at a particular temperature. It might have been in the electrical components section...

[SuperCow]

haha, its south for me, I live in Friesland, above Leeuwarden.
Your also welcome here, we will figure it out who comes where

I have an 1 pole temp sensor

0121.2 - Testing electrical components - B. Basic_nat. version standard (CH_S_I) KE II; Engine 1.pdf

Page 2, the picture B11/3

Seems I have the M102.962 NV (KAT/RÜF) version.

[Stretch]

Well I don't know why I thought you were in Brabant - that's at least a whole lot less of the sodding A50 for me (or you) to have to deal with! And Friesland is also a chance for me to go and see continental classics - I've always wondered about that chap!

[Stretch]

Nice PDF by the way - but every time I look at instructions like that my eyes glaze over and I lose the will to keep breathing!