High idle.
 

1991 420SEL. High idle problem. Searching different sites for this problem and it always comes to Aux. Air Valve sticking. Seen picture of one but, don’t think mine has one. At least I don’t recall seeing one. Is there one and where would it be located?
Just replaced injectors, and holders. Removed , cleaned (really coked up) and replaced all intake manifold soft bits.
Replaced all vacuum lines and rubber ends.
Cleaned idle control valve and start injector valve.
Deleted AIR and EGR systems.
Lamda check, and fuel distributor controls checked SAT.
No vacuum leaks.
Runs smooth now but, high idle. About 1100 RPM when warm.
Thanks for any suggestions.

Would you mind pointing me to any DIY job for injectors clean as well as icv?

Are you sure the idle control is getting power/ functioning? When it quits, the car defaults to the high idle. This was the case with my '85 500SL.

The idle control valve is easy to check for the solenoid function. Just hook up two jumper leads from the battery and touch them to the two prongs on the ICU. If it clicks it works. But, it doesn't tell you if its sealing or not unless you hook a vacuum source to it. You could use low positive pressure instead. It's just a soenoid actuated on/off valve I tested on the bench. Hooked up a handheld minivac to it (with duck tape of course) and powered from a lawn mower battery.

Dave

U: Injector clean is easy. Just soak and spray with Carb. cleaner. ICU just spray the goes in and goes out ports with Carb. cleaner also. Spray 'till it run clean. Shake it in your hand to see if the plunger inside is free to move. You'll hear it click back and forth.
You can see the spray patteren of the injectors with the proper lighting and backdrop. Fill the goes in side with Carb. cleaner, then blow it out with your air hose and watch the patteren. Should be smooth and an even conical shape. I repeatedly cleaned mine and only about half had a nice pattern. There're only about $25.00 apiece new. If replacing, replace the seal, plastic holder, and O-Ring as well. My holders and O-Rings were as brittle as corn flakes.

Dave

Also check idle switch at throttle body ,its a 3 pin connector ,sits near idle control valve area, at idle 2 pins have continuety,i dont remember which 2 pins , but its easy to test,correctly functioning your idle should be about 600rpms

Also check idle switch , follow black cable from throttle to connector near idle control valve check with mulimeter 2 of 3 pins have continuety at idle

Replaced with new when I did the intake. Just because it's a be-ach to get to.

Only thing stopping me is to clean them is to get them.
Where are injectors located and how to get them out? Are they under fd.I will be opening fd to clean throttle body so might do this at same time.

If you are refering to the 420, they are located at the ends of the fuel lines from the Fuel Distributor. You will need to remove the black rubber hoses that connects to each Fuel Injector "holder".
Detach the each fuel line at both ends.
Remove the long rubber air hose attached to each FI holder.
The black plastic holder with the brass injector simply pulls straight out. UP.
Make sure the rubber O-Ring is removed from the intake hole.
Pop the injector out of the holder. You will see the injector "seal" that holds the brass injector in the plastic holder.
You will want to replace the seals, holders, and O-Rings. The O-Rings usually come with the new holders.
Don't be surprised if the holders crumble during removal. They get very brittle with age, heat, just like the rubber bits.
When reinstalling, clean out the holes in the manifold with a rag soaked with carb cleaner.
Grease the manifold holes and new O-Rings with a liberal amount of O-Ring lube.

Dave

Thanks Dave. That's what i was looking for.