I posted this issue yesterday form another subject link(ICV) but did not get a response. Perhaps because of the subject it was posted under. So I am trying to repost. I apologize for those who have read it already. Pls let me know your thoughts. I would really appreciate it.


1. Idle is oscillating when not in gear, but seems to diminish when idling in gear.The oscillation appears to repeat every 5 seconds and a cycle is about 1 sec. on the rise and another sec. to drop. The idle is at 750 and would rise to about 850, and would go back down to 750. When in gear, the idle is about 650-700. Since i am focused on the ICV, I also observed that the voltage accross the ICV terminals when idling and at park, also oscillates with the RPM, and varies from about 4.35V to 4.70V. The oscillation is not much but I suspect this is not normal, and would like to understand the probable causes and correct the problem.

2. My other problem is rough idle, both when in gear, and otherwise. I observe that the rough idle is more so when not in gear. The engine does not die, although very noticeable, more so like a cylinder is missing. It runs smooth otherwise and tranny shifts smooth, so far as I can tell.

Steps that I have done are as follows:
1. Cleaned ICV and replaced both rubber connectors.
2. ICV measures about 5 OHMS. Closes fully when 12 volts in applied.
3. Voltage accross ICV terminals at idle and in park is 4.35 to 4.7V.
4. Coolant temp sensor(B11/2 - 4 terminals) measures about 370 OHMS for each pair of terminals measured diagonally. This was after engine was idling for a while. Resistance measurement when cold was very high.
5. Throttle valve switch(S29/2) - The Normally Closed terminal measured 0 OHMS, but would open with a slight movement of the throttle. The Normally Open terminal measured OPEN, and would close only at full throttle. ( ie it stays OPEN intil full throttle is reached.)
6. Pulled the plug wires one at a time at the distributor cap, in an effort to isolate the cause of rough idle, but suprisingly, did not observe any change in idle ( worse nor better...). I do not undertand this behavour at all. I was expecting to observe the idle to get worse, but to my ears, it was the same. Can someone expalin this to me?

7. Next Steps - The air distributor hoses and crossover breather hoses are hard as rock. These may still be the original parts. I am going to replace the hoses plus the injectors, and holders, etc..

I would appreciate your inputs. I am trying to undertand scenario#6 above, the rough idle and the idle oscillation.

thx,
emmy

i will be watching what info people give you i am in the same boat with A 90-560SEL.WHEN MINE IS COLD RUNS ROUGH AND WANTS TO DIE ONCE UP TO RUNNING TEMP SMOOTHES OUT.

i do not think there will be any replies as my posting above is 2 years old. at any rate I did a lot of things to resolve the idle problem. All rubber were renewed, new plugs and wires, etc...One thing I remember was that there was one plug that was not installed propeply. I do not have that problem anymore.

Have the fuel system and injectors been cleaned? Have you tried different brand of gas? My 84' 500 SEL would be hard to start when I used Chevron but the problem goes away as soon as I fill the tank up with Union 76 - very strange!

why did you repost if you no longer have this proublem?:fork_off:

I did not re-post it. Johnlo responded to my post back in 2005. Pls review the trail.

cheers,

johnlo,give us some idea's as to what you have done to try to fix it? First I would look at the plugs,and wires make sure the resistance is not to high in the wires,but the fact that it smooths out when warm,makes me think of air leeks,(vacuum) the best thing is to do is a smoke test,find the leek,check the idle air lines they get hard with age and are not good at sealing if not pliable. It seems that you are pulling to much air,Though you m might also need to look at the EHA and the on off ratio,If you are not having a search problem at return to idle (deceleration) then the potentiometer is probably not bad.Well try some of that for starters,JNT

sure guys new plug wires rotor cap replaced all of the vaccum fittings and hoses. did a check with carb cleaner around the injectors got a hit reved up the engine, so need seals on the injectors. i just switched the ones in a 380 a year ago so i plan to use those but how do i get the seals off the other injectors?

after you used starting fluid,or carb cleaner the chance that(if) you had a weak seal it will show up in a week or so,the money is not that high for new seals, just replace them with new.Smoke test is the best way to go for leek testing. did you replace the idle air hoses?they get hard and will leek also the air plenum but you might just try the seals (injector) for now. let us know how you do!JNT

did repllace hoses are you talking about the ones at the icv? those have a small split in the top one.

Said the blind man.I better look more closely before I speak!

Yes they are notorious for leeks,when aged,they get hard and no longer keep a good seal. You may benefit from looking at a post I did on intake vacuum leeks,I rebuilt my wifes 420sel intake,replaced all of the rubber,including the plenum chamber,and injector seals as well as the injector cups, I got a used icv on line in parts for sale.If any thing the car idles to low now,but I also did some resetting of the EHA, and the POT. needed to be replaced. the mileage jumped up by 1.5 and the power is much better too. look up jim16671836,he may stll have a used one if not do the parts post for a used one.JNT

Just worked through IC Valve replacement and the rubber fittings on a 500SEL, it now idels too low at about 500rpm and is hard to start compared to when it had the faulty ICV. New leads, cap, plugs and the old ICV was shot. Any suggestions how to raise the idle on these? It seems from prebious posts its the black art of voltage checks and no sign of a mechanical adjustment for such an apparent simple problem. Any advice would be appreciated.

now that you have fixed the air leaks the engine is pulling harder on the plate and the mixture is probably too rich.try backing off on the 3mm at the fuel distributor but do so in small increments.[somebody adjusted it previously to cover the problem of the leaks].

__________________
David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

David, Once again thank you for the fix. Adjusting the mixture has made no difference, leaner it stumbles and same with richer. Tried adjusting the linkage to mechanically increase revs, however that just seemed to make the gear change harsher with no measurable rev increase at idle. Will try and hunt down someone in Brisbane that knows these and see if I can get it fixed that way. Oh for an early Holden with a single barrel solex!