Mercedes Benz repair: mercedes 560sl, oil pressure gauge, mercedes 560sl

Question
QUESTION: I believe I may have an electrical or fuel injector problem.  The engine starts readily when I turn the ignition.  However, as it sits and idles the RPMs gradually slow to about 500, the engine almost stalls, then the RPMs race up to 12 to 1500 and then drop again toward 500.  At the same time of the slowing then racing of the engine I hear a clicking noise inside the car that seems to be coming from the passenger side under the dash.  The clicking starts when the car hits the lower RPMs and when it hits the higher RPM range, it sounds like a switch going on and off.  The oil pressure gauge goes up and down as the RPMs increase and decrease.  The needle bounces toward zero as the RPMs hit 500.  Underneath the hood there is a red light that is blinking on the electrical connection box on the driver side.  The check engine light on the dash also goes on and off as the engine RPMs go up and down...belive that may be due to the inconsistent oil pressure or as a result of the blinking light.  Though the temperature gauge is normal, the manner by which the engine labors and then races would lead one to believe the engine was overheated were it not for the other symptoms.  I do not believe it is as issue as the speeding and slowing take place as soon as the engine starts when it is cold or warm.  If I drive the car, all appears normal until I take my foot off the gas and let is slowdown to stop at a light, then the engine will go back to nearly stalling and then picking up speed to the 1200 to 1500 RPM range, which is not good when the car is in gear as the car will lurch.

ANSWER: check your ovp relay it sounds like its gone to the dodo..it is by your passenger side firewall it has a 10 amp fuse in it.. you should be fine then...it sounds like the ovp relay is making your engine surge stop.I have a 560 sel and the damn car when I bought it would start up fine then would run really high like 3k in idle..i could chirp the wheels going in reverse changed the fuse and all was good bought the car for 500 dollars and put about a dollar into the 10 amp fuse.. good luck if you have any other questions email me

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QUESTION: Shane:  Thanks for the insight.  Yesterday I went down to the car to replace the fuse.  I took off the foot plate on the passenger side so I could take a look at things...I started the car to warm it up while I was locating things....the engine ran smoothly.  I let it idle for 10 min....it ran smoothly...I took it out and drove around...it ran smoothly.  I then parked the vehicle....came back three hours later...it started out fine..but as I drove it a bit, the engine started to race a bit when I took my foot off the gas to slow down as I glided toward a red light.  Then at the red light it got into the RPM up and down cycle.  I drove a bit more and things leveled out for a while...got back to the parking spot and it raced a bit before I turned it off.  I did not change the fuse.  Based on the above was wondering if that changes any of your thoughts.

Answer
try changing the fuse or the whole ovp relay in itself bad idle surges are common when a ovp relay is shot or high rpm I would just replace the whole unit google ovp relay on your car and you will find a shlew of sales people and you will also find where it iswhat it looks like