I had the Low Idle and no tach problem and found that it is typically the OVP relay.
I pulled out the OVP, took it apart, resoldered the internal connections, reassembled it and reinstalled.
Problem solved for about a day, then reappeared.
Went ahead and bought another OVP, 'used but tested' and this also did not solve the problem. I put in a new fuse too.
If I plug in the OVP (either one) while the engine is (barely) idling there is a very short return to normal idle, barely noticeable but still noticeable, but then the idle drops back down immediately so low that the engine shakes. I can repeat this over and over, it happens just as the connections are made to the OVP when I plug it in, but the effect is ultra short before the problem reappears.

This has me stumped, any takers?

Thanks in advance,

Dan

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1985 Mercedes 190D, 2.2, Standard Trans.
~230k Mi.
Visalia - Central California

(Left the Aluminum Hat somewhere)

That tells me there's still a loose connection,somewhere...
"Temporary Fix", Isn't.
Re-Check your Re-Solders.

'How "Clean Bright and Tight" are the Pin Connections? Inward and Out.
Removing and replacing the OVP IS RESEATING ZomeZing correctly,however
short term.

So,When you R+R the OVP, for an instant the EDS is getting the "Correct"
Voltage and Regulates the Idle Control properly...

__________________
'84 300SD sold
124.128

Use a voltmeter of test light to see if current is flowing thru the OVPR.

With the relay installed but lifted slightly check for power at terminal #87

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks, but which one is number 87? There are 5 metal pins and one hollow plastic pin (what does that one do?)
Is there a diagram or other way to determine #87 ?

__________________
1985 Mercedes 190D, 2.2, Standard Trans.
~230k Mi.
Visalia - Central California

Should be a diagram on the side of the relay

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Ok, was able to test voltage at pin 87, key on but engine off, it was 9 volts, I take it that is not enough?
I also tested at the battery with engine on at ~2000 rpm = 13.96 volts, so that checks out.
So where do I look now?

__________________
1985 Mercedes 190D, 2.2, Standard Trans.
~230k Mi.
Visalia - Central California

My 190d is having an idle problem. What is the QVP & EDS?

Hugh Sr
1984 190d 98,433

OVP Over Voltage Protection

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

E.D.S.
(Stuttgart's way of Obfuscating engine computer controls)

__________________
'84 300SD sold
124.128

Ok, now I have a new OVP, but it didn't help at all :-(
I have also checked voltage on the EDS which the OVP supposedly supplies with power and got a solid 12.08 volts.

What gives????

__________________
1985 Mercedes 190D, 2.2, Standard Trans.
~230k Mi.
Visalia - Central California