OVP relay symptoms?

the car is a '89 300E, I am beginning to wonder if I'm also having a problem with my OVP relay. The car idles, in gear, around 500 rpm and in neutral
around 700 or 800 rpm. My wife tells me that occasionally she is losing power. Yesterday it happend to me, the engine choked repeatedly but by fiddling the gas pedal it recovered and zoomed away (probably would have done so on it's own anyway). The 'fuel consumption gauge' indicated sky high vacuum while engine had no power. Tried car again this morning when the engine was ice cold and there were no problems (could be fluke I guess). So, I'm guessing engine chokes after it warms up and goes into closed loop mode. The clincher was when my wife tells me that the ABS light came on the other day while driving.... are these symptons beginning to fit those of an OVP relay? IF so, should I simply replace or try to resolder the connections?
cheers, guenter
ps also plan to take apart and clean the ICV this weekend... I'm hoping that spraying WD40 in there should help
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Guenter Scholz wrote:

Don't try resoldering, it's not the connections, it's the relay solenoid or contacts that have failed/worn. Of course, check the fuse first before replacing.
Just get a new one and it will be good for the next 10-15 years. ;-)

Hm, good luck!
Cheers, ws
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Can't say for the choking, but the ABS light is a good indicator. OVP relay provides 'controlled/protected' voltage to ECU, ABS brains so those expensive parts will not be toasted when bad thing happens (for example, wrong polarity when jumping the car). ABS light is known to turn on when voltaage goes wild.
Resoldering won't work. Like this other poster says, it is not the connection. It is the aging of parts inside.
Guenter Scholz wrote:

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thanks for that... I checked the ICV today and it was clean and operated just fine when I connected it directly to the battery... all air hoses connected to it were good. Now, does the valve open or close after the car has warmed up?? I see that with no power applied the valve is maybe 1/4 open, but in the sense that it's 'past' closed. ie, when I apply power slowly the opening will ... on opening completely, first close and then continue to open all the way.... in a sense the valve is initially not simply closed, but actually rotated a bit beyond that so it's about 1/4 open again.... does this seem right???
it seems that the ECU provides a controlled ground and when the engine is cold the circuit is open.... on warming, presumably, the 'ground' resistance decreases allowing the bypass valve to progressively open. Is that analysis close to what happens??
thanks for any information
cheers, guenter

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Gόnter,
Before you go to that expense have the battery checked.
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,,.... thanks for that, good idea. The battery checked out just find. The Idle Control Valve (ICV) also appers to be OK,. Do you have any idea hpw this valve operates in general? Does it open or close after the car has warmed up for example
cheers, guenter

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    Indeed. Looking at this setup some more this afternoon and testing voltages etc. I believe the way it works is as follows.... hope someone who knows better will comment on this analysis.
the ICV appears to be a rotary solenoid valve. The valve opens and closes in response to a signal from the ECU and provides a 'fine' adjustment to the idle. (my 300E idles well when cold so that there must be a cold bypass valve to give a higher idle before warming up. When engine has warmed and is controlled by ECU (closed loop) the ICV will compensate for minor load variations the car's idle by rotating a bypass valve within the ICV. Electrically the hot is always on (over 13V) and the amount of voltage the ICV gets appears to be adjusted (by the ECU) in the ground leg of the circuit. The larger the voltage (ie the smaller the resistance to ground) the more the valve opens and the higher the idle. the valve responds essentially instantaneously judging by how the rotating 'plug' whipps around when applying dc directly.
So, after getting the car good and warmed up my idle is low 'under load' but normal in P. Measuring resistance to ground from right side socket on the ICV plug gives very high resistance.... therefore no voltage will appear across the ICV and it remains in one position and does not respond to any load variations. I noticed earlier that this position is actually 'past' the closed position by about 1/3 of the total opening. Pulling the plug off completely reduces idle a 'bit' more, but essentially stays around 500rpm or a bit below.
Any comments anyone?
cheers, guenter
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