I just recently replaced the motor in my 1994 C280 and its idling between 1500-1700 rpm when it warms up...when you first cold start, it idles and then shuts down..but it will start right back up and idle fine..but as it warms up the rpms rise to 1500...when the car is placed in gear the rpms drop to 700-to 850 rpm..the asr light is on and the check engine light just came on...the car runs great other than the high idle... I didn't have any of these problems with the old engine..I replaced it because of a blown head gasket...any suggestions on this are welcome

Chance are that you either blew the fuse of the Over-Voltage protection relay, and/or the OVP relay is defective. Check the fuse on top of the relay first.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

I replaced the ovp and I'm having the same problems..1800 rpm in park and 900 rpm in drive.... ASR light stays on...check engine light turned out to be EVAP...

It still sounds like you have a problem with the OVP relay, or possibly with the associated wiring. However, before you go on and replace any additional parts, start with an easy thing first.

a) Check your gas pedal, its cables, and linkages. Make sure none are too tight.

b) Pull your accelerator pedal back by hand. See if that makes a significant difference to the idle speed.

If that does not work, than electrical diagnostic steps are next.

Phil.

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'95 E300 Diesel, 264,000 Miles. [Sold it]

I went thru the mechanical basics with no change in the idle...I read some other threads and it mentioned disconnecting the OVP to see if there is a change...there was a drastic change...vehicle shut off...and after I plugged it back in..the car starts without the ignition switch being engaged...I let the car sit for 10 mins and it went back to starting properly...i went to drive the car and the starter engaged again while i was driving...i put water on it to see if I could kill the gremlins but it didn't work...

Pull out the big black plastic cover on the firewall, behind the Battery, and look closely at the engine wiring harness, the electrical plugs, and the relays that are there.

Pay special attention to the wiring harness. See if it is intact. Jiggle the wires, the plugs, and the relays a bit, and see if that makes a difference.

If you are careful, you can do this with the engine running.


Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

car is driving me crazy... I pulled and tugged on the wiring and nothing changed...while working on the car today the starter engaged in the run position on ignition switch... did it a few times and then stopped...i decided to check the fuses and the reverse light fuse was blown...I had the ignition in the run position so i could check fuses and when i went to replace the blown fuse for the revese light the car started...with me standing outside of the car... everytime I tried to insert the fuse the car would start.