W126 560SEL high/strange idle
 

Hey guys,

I've had this problem for a while now, and I'm about to put it in the shop, but I was wondering if you could help diagnose this issue.

My '87 560SEL has always run a little weird after it sat for about 8 months, but lately it's been doing some strange, strange stuff.

This is all after cleaning the IAC valve, by the way.

-When I start the car cold, it idles at around 750, which is okay, at best, but once I let it warm up, it fluctuates at around 750 to 650, going up and down between the two.

-When I drive it around town, or any time in general, the cars idle lowers and the economy gauge goes to the middle, and sort of 'rumbles' when I hit the breaks (only when lowering speed between 25 to 10 mph).

-When warm, car shifts really hard into drive or reverse; I depress the brake fully every time, and always put it into neutral for about 4 seconds before I shift, and it still does it.

-There is a slight whistling noise coming from the left of the engine compartment when I first start her up in the morning, which makes me suspect a vacuum leak somewhere in there.


If anybody has any ideas, it is greatly appreciated.

(also, the idle problem could definitely be the ICU, but I've taken it out and the idle surges to almost 2000; I dunno.)


Thanks

I'm with you, sounds like a major vac leak, and probably in the vac line going to the brake booster.

That's exactly what I thought was going on, I've never diagnosed one of my issues before and I don't want to go the mechanic throwing money around at things I don't know what I'm talkin' about.

But the brake booster vacuum wouldn't be causing all of those symptoms, would it?

I figure it'll probably affect the idle speed. grumbling and whistling, but would the vacuum affect my shifting too?

Or would it be almost like a chain reaction, where the problems fix each other like this:

vacuum -> idle -> shifting

Thanks again

I can't remember the exact name, but there is a vacuum line running from the manifold to the transmission, IIRC it's a modulator valve, designed to 'cushion' the harshness of the shifts. See if it's disconnected or has a crack in the rubber connector at either end. It's adjustable too....do a search, many posts on this.

So to check this modulator valve, would I have to raise the front end of the car? or could I try and crawl under there and have a look see?

I'll probably check it out sometime tonight.


As for my research, the line should be on the left side of the transmission, and I'm looking for a crack in the grommet or whatever it is that holds it on.

I'll try and take pictures for documentation as well.


Thanks

It would be much easier to raise the car and have a close look, although you might be able to peer up and check it from the ground. As usual, jackstand(s) are mandatory.

Sounds like you have the typical vacuum leaks on this car... intake manifold gaskets, breather tubes, etc.

Look for the obvious, but think of it this way: would you drive on 20 year old tires? No. Same for the rubber under there, it's simply rotted out due to heat.

I had a strong feeling it was a vacuum leak; thanks for confirming my theory.


Now the question is: how much will it cost to have all those hoses replaced?


Thanks again, guys

Blatantly obvious when the "ECONOMY" needle is in the center. Left is high vac (normal)... right is zero vac (WOT or severe vac leaks).

No clue on the labor, probably not worth paying someone. There are eight o-ring donut looking dudes that seal the upper to the lower that seem to go bad also, these are a REAL pain to deal with as the intake between the heads ALL gets to come out. Start looking over the factory service manual, it'll give ideas.

But I'd guess if you took it somewhere you're looking at an easy day to two (say one and one half being 12 hours) @ $100/hr so that's $1200 in labor plus parts... parts shouldn't cost much more than a few hundred.

Need vac lines, breather tubes, intake gaskets, the o-rings, fuel injector seals, the fuel injector cups, fuel injector breather tubes, probably the fuel distributor to throttle body boot, etc.

No real point in doing it halfassed if you're that far in there. I'm not sure what you want to spend nor how far you're willing to go once in there.

High Idle condition....
 

I am coming across is the car is idling quite high. @1300-1600rpm , not fluctuating but steady fast idle. I cleaned out the IAC and replaced alot of the vacuum elbows. I even tried to adjust the Air/Fuel mixture but that does nothing and aids in a no start again obviously if it goes too lean. Do you have any ideas? I cannot even locate an idle control relay that some people state that the car has.

spray FI cleaner around all connection 1st arount intake manafold, then vac line's. When car idel changes that where to look.

ICV Cleaning ! is bad thing
 

Hey! here is a little help......
You might have an other problem other then the ICV (Idle Control Valve) BUT
i can tell you one thing, this valve CAN NOT BE CLEANED!!!!!! many people try to clean it and that make's your car got nuts right after...
I will explain why. I did a couple try's with 3 ICV's from 3 different used cars, the rubbers seals inside will leak and break as soon as you shoot brake cleaner, intake cleaner or what ever else in there. I even tried to clean one with some Q tips to see if it would work and after every single time i touched one(cleaning wise) it stopped functioning properly. So ICV cleaning is not possible with W126's. ICV's it will not respond well and break (even tho current is still going through and looks like it's working it wont work well)
I bought 2 brand new one's one for my '87 420SEL and 1 for my '88 560SEL
for the 4th time i tried cleaning and "new one" even tho it didn't need cleaning, and BOOM guess what it was defective right after.... (i got it refunded and ask for an other one:D:cool: i know... i know...)

So do not Clean your ICV.... Actually this weekend i have a Costumer with a '90 560SEL with the same problem(high idle) coming to get his car fixed. If it's not his ICV it's a vacuum leak but, best bet is the ICV.