90 560 SEL, several questions

Just purchased my first Mercedes, decided to go with the top of my wishlist and went with the 1990 560 SEL. A couple of items need repair, so I thought I would pose questions to the group and see if anyone has experience with these. Just for background, this car has 190,000 miles on it.

1. Sunroof.. Power sunroof does not open. Fuse appears good, same fuse as front seat heat, heat works.

1. Engine misfire.. Car seems to be missing on one or two cyl, still drives well, most noticable at stoplights.

2. High idle.. Wants to idle at about 2000 RPM. Can't be normal, this means that I can take my foot off the gas and still maintain 40 mph. Also results in some very hard shifts into drive or reverse.

I have not purchaced a service book for this car yet, will be looking for that shortly, but any suggestions in the meantime would be appriciated. Thank you in advance.

Aaron

High school -1999.... Firm believer that Mercedes were for yuppie scum

These can be very hard to fix, especially if total disassembly is required... The motor is in the trunk on the drivers side I think. You should here it trying to turn when you actuate it?

Could be anything from bad gas to poor compression.

Uh OH. This sounds like someone jacked up the idle to cover the missing...

Trouble I bet. I would carefully inspect all underhood areas, looking for leaking vacuum hoses or cracks in the air intake system. Also inspect the air cleaner element for hints.

Pull all the plugs and see what they look like. Oily? Fouled? trouble...

I doubt they would. jacking up the idle on these cars is such a pain you might as well just fix the problem. My guess is idle control unit. Expensive if you buy new, not too bad if you get it from a salvage yard like pgauto.com Richard

Check to vaccuum hoses and try carb cleaner inside throtle body. An Ohm meter check of spark plug wires is in order.

The idle solenoid is in front center under air cleaner. It has two wires connecting at end. Check the wires for breakage, they have broke twice for me causing the 2000 RPM idle. Otherwise, the only other item controlling idle is the idle control module.

-Kent

Check for voltage at the motor (in the trunk, on the right up a bit)

I am a bit late...

Check voltage at the motor... while someone is pressing the button to open. If power is there... then motor is bad... if no power, then replace the fuse and check again. Fuse may look good but when you remove it, falls apart or corroded.

Sounds like spark plug wires are bad... common. check resistance (ohm) should al be below 1400. Otherwise, you probably need to change the cap and rotor.

Check for vacuum leak... In front of engine, there is a round device with a wire plug in front and two big vac hose in rear at 90 degree... if you remove the electrical plug and the engine revs higher... most likely to be a vac leak somewhere... trace all vacuum hoses.

Actually it turns out he was correct. After an adventure with a misfit, I found a competent mechanic who removed the air cleaner and found that the plug covering the idle adjustment screw had been broken off and the idle turned up. Upon turning it back to normal, the car refused to start, back up and it started, back down and it vented black exhaust. The vehicle is at the mechanic to be fully inspected... could be plugs or wires or distributer or fuel injectors.... or.....? Wish me luck, I don't want the car I have coveted for years to become my nightmare.

OK, here's where we are now.

All 8 spark plugs are black and sooty, acording to the mechanic this indicates a fuel delivery problem. He says the wires and distributer appear to be in good condition, and that the compression is excellent. Also, no vacuum leaks. Possible causes according to him are as follows: Fuel pressure regulator Fuel Distributor Computer Electrohydrolic actuator (what?!?)

Next stop for the car is an authorized Mercedes service center as the mechanic has the decency to tell me he did not have the equipment to isolate the exact problem. So far, some good news and some bad news, two mechanics and $160.00 US

Aaron

Dude! You are doing great! Good compression and a fuel issue is a happy story compared to what it might have been (ie major mechanical issues).

Brace yourself for the bill from the dealer and pray for it to be the pressure regulator...

Sounds like you also have found a good honest mechanic there. Stick with him, they are rare.

could be, I've not had the car long enough to know it's ins and outs. How does one set that? The car also leaves quite the cloud of black when accelerating

To do it proper you need a multimeter that measures duty cycles...I'll do better than describe it I'll give you a link with good info. It would only take a mechanic a couple of minutes to set it...though if you do have a mechanic do it go to an independant shop cause the dealer will charge you 1 hour labor.

Wow, that's pretty complex. I would check the fuel pressure regulator first, since that seems a lot simpler?

Marty

PS Presumably this setting wouldn't just get way too rich on it's own. I wouldn't touch it until verifying everything else, or you will screw it up and have even more problems.

Maybe I should have just presented it in simpler terms: get a 3mm long allen key and a multimeter with duty cycles. Stick the multimeter prongs in pins 2 and 3 of the diagnostic port. Stick the allen key in that hole with the rubber seal in the air filter housing, and turn it counter clockwise until your multimeter reads 70% (note how many turns it took in case you want to go back). Richard

Sounds to me like "little old lady driving powerful car, only to church, and to the market syndrome"......Change oil and filter and install "proper" new plugs, change air filter, add2 bottles of Chevron fuel injector cleaner, and go for a 200 mile ride on the interstate..... flooring it, when ever prudent. recheck

well, the car has 190,000 miles on it, so it must have been a long way to church =)