Gosh darn it!!!!! (Censored)
 

Well, I got my new OVP relay today, this new one had 2 red 10 amp fuses instead of one fuse, and it also had 2 more metal pins at the bottom, I swapped them out.............................. and...........







Nothing, the car still idles at 500 when in D gear........ :(

Back to the drawing board....... :o


Lemme get a little more specific with my problem...

When cold, meaning engine is cold...... thermostat at minimum....
The car starts up, settles at 500 RPM.
If I tap the accelerator immedietly and raise the RPMs to 1000, then let go, the engine then surge down and up, sometimes it stalls, sometimes it evens out...

If I hold the pedal down and keep the RPMs at about 1000 for a few minutes, until the temp gauge reads 60 C.... the RPMs will almost always settle at 600.... then I can put it in drive and the RPMs lower to 500....

I have noticed that once I get the car at operating temp.. (80 C)
The idle RPM in drive is 700 to 800 RPM, and in drive it is 500 again....

Anybody with ideas.... I have heard about EHA adjusting, but I do not have a voltmeter and I dont even know where the EHA is, or what screw to turn?!?!!

I also got two new vaccum hoses, which I will change out pretty soon, see if I can find a leak in the vac system....

You have classic signs of vaccuum leaks. get a 6 pack, bright light and look at everything.
Probably multiple leaks

Rahulio,

Have you tested the coolant temp sensor?
It is the last sensor on top of the valve cover,back of the engine compartment. http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1FX0MB1RS1GB0YO1R3&year=1989&make=MB&model=300-E-002&category=C&part=Water+Temp.+Sensor&appEngines=_any

You will need to buy a multimeter to troubleshoot this.
Only costs about $30.00 for a pretty good one.
To be most usefull for your car you will want to get one that has %duty setting, Ohm's setting, and 20Amps setting, as well as the usual Volts.

Marty

I asked this question earlier, but no response. How do you test this sensor with a VOM?
Mark

What kind of car? ...and...
Is yours 2 pin or 4 pin?

If 2 pin you test for Ohm's across (either way and reverse to double check)
a 4 pin I would have to investigate.
Here are values for KE:
Water temp sensor for KE injection system
Temperature °C........Resistance kΩ
-20........................15.7
-10.........................9.2
0............................5.9
10...........................3.7
20...........................2.5
30...........................1.7
40...........................1.18
50...........................0.84
60...........................0.60
70...........................0.435
80...........................0.325
90...........................0.247
Same resistance values apply to KE intake air temp sensor.
I think this chart applies to these 2 sensors for all KE systems but don't know for sure.

My Bad!!!
 

Hey guys, this afternoon, after I came home from school, I found my box at my porch containing my new OVP, and 2 breather hoses....

I replaced the OVP immedietly and was disappointed to see no difference when I restarted the engine...

But I went back after the car's engine was cold, and guess what?!???

My surging, and 500 to 300 RPM idle is gone! It now idles like new at 900RPM...

BUT... since I tried it in the afternoon and it does not work, I have concluded that I got my cold start enrichment back!

I now suspect the coolant temp sensor... could this still be the culprit for the warm engine conditions? Thanks!