all the info i can find online and some reading on here say the ovp on my w126 90 560sel should be a red top with 2 10volt fuses. Mine in a black top with 1 10 volt fuse. do need to replace my vaccum hoses but can this be causing the no/rough idle problems i am having? i have cleaned the icv per instructions on here and it was nasty! my hoses are cracked in a few places too.

Probably not, unless the problem is alot worse with the engine cold. As a test you can start the engine and pull the fuse on the OVP and see if it changes anything in the rpm or idle. Never heard of much probs with the OVP on 107's, matter of fact I answered a thread last week for a guy who couldn't find his, neither could a competent tech or two!
Gilly

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this one is a 126 chassis- but it wont start without the ovp- with it you have to keep your foot on the gas or it dies. While keeping your foot on the gas it idles very rough. i read quite a few posts that said the cracked vaccum lines can cause a rough idle. But my question is can it cause it to have no idle at all? The other thing is the top of my ovp is black and only has one 10 v fuse in it- when you look up the ovp for a 560 it has a red top with 2 10 v fuses. It must be an original ovp cause it has 6 06 1990 on the side of it? All for replacing parts to make the car perform bettter- but right now just would like it to be drivable.

I wouldn't get too hung-up on the OVP, it sounds like you have more basic problems. Cracked idle hoses will usually give you a fast idle. I think you have a major vacuum leak - possibly the EGR valve, or your mixture is really off, or your timing is off. There are plenty of posts on all of these.

Some stuff to try:

Can you get a vacuum reading at 1000 RPM? What does the dash 'economy' gauge show?

Can you put a timing light on it? What do you read off the balancer?

Check your EGR valve by putting vacuum to it and see if the "idle" gets even worse. If it doesn't, it may be stuck open.

Try going 1/2 turn clockwise on the mixture screw and see if that helps.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

appreciate the advice but forgive me i am not real savvy with all of the info you need. friends and brother in law hlp me and they do the real troublle shooting i mainly report. what kind of vaccum do i use. do not have some of the vaccum lines hooked up my disc is pretty confusing and none of us can find where 2 of the thermo vaccum linesd go.the same with the egr the vaccum is this common that general mechanic knowledge would know? i really appreciate everyones help i love the car but i need to be able to count on it, really do not want to give up on it.

You'd BETTER have those lines plugged then, if they're just disconnected you're losing massive amounts of manifold vac and your engine WILL run like crap if it runs at all. I HIGHLY suggest you find out how those lines should be routed before proceeding further.

I agree with all of the previous post. The engine should run without the OVP, just not very well especially when cold. The injection will run in emergency running mode, it will actually run without the engine control module installed at all in this mode. I'm a thinking the mixture has been messed with to the point that it won't operate in this mode, just with the module adjusting it, and even then won't run worth a hoot. There is the tall housing on the air horn that has a ball on top to seal it, has an adjuster inside and that's what adjusts the mixture, does it look like this "adjustment tower" has been damaged to allow some nut to mess with the mixture? By description of the problem I'd look at that first, and if it needs repair do that then determine if the idle system is also in need of repair.
Gilly

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i understand where the mixture port is but i do not have a ball on the top of it.i live in a very small town and the previous ownert took it to some one locally so no telling what type of "country inginuity" i am dealing with. do i just keep turning the mixture clock wise until i get it right?