it was suggested on another thread today that the clicking in the ACC switches is not electrical at all, but symptomatic of low vacuum due to the car not running right because of a fuel starvation issue. any thoughts?

Unbelievable, I changed the OVP in mid-March, the car seemed to run OK for awhile. It started acting weird again, so I let my stellar service dept work on it...they "cured" the problem with a fuel pump relay and yet another OVP, they said the one I had just put in was defective. Today I picked it up from service, ran great for 15 minutes, then right back where we started, the idle speed is all over the place, mostly higher than I would prefer, 1650 RPM's give or take, and wants to stall below 2000 RPM"s under anything but really light throttle. I almost didn't get home this PM. I can change parts blindly, but this was a Mercedes tech who has been working on these darn cars for over 20 years...I gave him as much information as I could, and still I got a crap result. Given that it tends to run OK for 10-15 minutes, then the idle fluctuations and stumbling tend to start, I'm thinking something electrical is overheating once the engine gets up to temp. Or is the fuel pump overheating? Even in park, if I goose the throttle when it is acting up, it will stumble and sometimes die. If the car dies after I hit the throttle too hard, it doesn't want to start for 30 seconds or more, it it dies without throttle application, it starts right up. Any thoughts?

On the subject of the high idle, I pulled the klima relay off and plugged it back in, the idle speed hovered around 1000, much lower than the 1600+ I had seen just prior to that. I searched klima and saw all sorts of threads...I have a pretty clear understanding of the OVP relay's purpose now, but I'm still not entirely clear on what the klima does.

I would be willing to bet is none of the above ... I would, of course, want every penny back from the service ... sounds like they, too, were experimenting with parts.

Water is weird ... will get in strangest places and force other debris inside the engine compartment ... did you pull and reconnect every connection you can get at? All the relays? Check fuses for broken one (you can't tell many times until you pull them out then they fall apart).

Good grief, it got wet 90 days ago and has been driven 1500 miles, I guess since, with varying levels of success in having it run right. It'll run at 70 MHP with light throttle all day, but getting going from a stop, once it is warm, and has been warm for 10-15 minutes, is the issue. This is maddening.

I did notice a new defect today...one of the vacuum lines to the ICV is split, never noticed that before.

Blinking Recirc
 

Check out whether your stumble/clicking happens if your climate control is shut off. I was on http://www.peachparts.com/ the other day checking out a blinking recirc on my 420. A thread there advised disconnecting the electrical heat pump under the wiper fluid tank on the theory that this pump freezes up, creating a voltage issue with the climate control and also affecting the fuel pump (rough running). Apparently disconnecting the electrical heat pump avoid the voltage issue. In my case, I was having the clicking and blinking a time or two, especially first thing in the a.m. when the engine was cold. It makes sense that the electrical heat pump would then try to provide heat right away. My car would crank and crank and crank before finally starting. When I then tried starting if with the CC off, it would start normally. Abusouk

I'll try that in the AM...this whole situation is making me want to scream. I"m also going to pull all of the fuses and replace the whole shebang with fresh ones. The third item on my agenda will be to check every electrical connection under the hood, take them apart, put them together, pull all of the relays and re-seat them. The common thread here seems to be that it runs OK, as a rule, until it is up to temp, and has been for at least 10 minutes. The trouble starts when I feel/hear what almost feels like a switch tripping, like a little thump, sort of like a small door closing, then idle gets lumpy and it wants to stall. Is the high idle a symptom or an unrelated issue?

In the meantime I'm driving my tired, ugly, rusty SL that needs twice as much attention as the SEL to be a decent long term car, trying to nurse it along until the SEL is back to life, then I can spend a king's ransom on the SL. The irony here is that the SEL looks great, shiny white paint, new Continental tires, sitting tall and proud...it looks well kept. The SL is rusty and nasty, torn up seats, leaks PS fluid like there's no tomorrow, but at least it starts and gets me to the office.

OK, I played with it today...let it get up to temp, the idle speed was 1000ish cold, gradually climbed to 1500+ as it warmed up. I pulled the klima relay then plugged it back in the idle fell to 1000-1100. I pulled the plug off the ICV and the idle jumped immediately to 1650 or so, plugged it back in, it fell to 1100 or so. I was hoping it would stumble or act up, but it didn't, except for the high idle. Any thoughts?

check the voltage @ your ICV.. If it's greater the 4v or so your ICV isn't working properly which I'd wager is the cause of your high idle..

Jonathan

I may just lose my mind...had one of the apprentice mechanics come to me at work today looking for hours, so I told him to change the plugs and wires on the car...he did it, double-checked everything, tried to start up, and it has a horrible miss, won't hold an idle at all, and won't even start without lots of cranking and working the gas pedal, let go of the gas and the idle will drop until the car dies...the recirc button on the ACC panel is blinking on and off and clicking like mad the whole time. I'm going to guess he did something with a vacuum line. I got so disgusted that I told him to wait until Monday, we'll deal with it then.

If it were my car, I'd go the local Catholic church and inquire about an exorcism.:D

First thing I would do would be go back and Triple check the wires/cap/rotos/plugs etc.. What you are describing sounds like Classic mis-matched wires..

Best of luck.

Jonathan

we checked the wires twice, gapped the plugs exactly as directed by the MB service manager, still runs like crap. At least I have other cars, but I have to resolve this eventually.