I watched your video. My '88 M103 does the same thing (tach and vac guage fluctuations) and mine has only 59K on it. I thought it was 'normal'. I average 20mpg.

Why .65 volts? Is because my dad has a 86 300e that still runs like it came right out of the factory in 86' and that thing (still trying to buy it) has not been touched in any other way except for oil changes, sway bar bushings, etc,etc, simple crap.

So I use that car for specs and it was pinging .65 volts when the engine was at a warm idle. His car will chirp the tires if need be..............(jealousy kickin in)

Now down to the adjustment, for someone that has never done this it may take you a couple of times to get the adjustment right. I'm posting a link here to give you an idea since i'm more of a hands on guy to show you how to do it, but since im not there this will have to tide you over. If you have any questions feel free to ask.

http://sg-motorsports.com/AFS%20Pot%20write-up.htm

And the sensor you can get it seperate, but it takes alot of searching cuz there is still a handful out there. But once their gone its the whole housing you got to buy.

Oh and after I just put mine in my car, it grew its balls back! :eek:

so I didn't see where you replaced the spark plugs...maybe I missed it...I saw something about NGK spark plugs....very bad!!! my 1990 300TE was idling like crap, stalling, hard warm start....i did the basic checks...idle control valve, O2 sensor, low tension electrical connections, inspected the plugs for gap and regap-ed (they were Bosch of acceptable spec)...i replaced the fuel distributor and the coolant temp sensor (because the engine would always start cold just fine and get worse with warm-up)....nothing...problem kept getting worse....finally i said screw it, this feels like ignition and went and bought a set of the new Bosch Copper-Pluses for $25 and threw them in...car ran like a champ right on first start and has since for 2 years...i swear this is true...it was spark plugs

my point is that i looked right through the solution because i thought it couldn't possibly be something that obvious...gotta be something else

Yeh I've done all the basics like that...I have the correct H9DC0 non-resistors in. That is why I am out of ideas at this point :)

Does anybody know how the potentiometer influences the KE-Jetronic system? I'm just not sure if the rough idle and the fluctuating rpm's are from the same cause. Either way one knocked out, if not both would be great.

I will definitely use .65v as my benchmark. Thanks.

Mercedes recommends .51volts to .81volts(on pins 1 n 2 ), I used the .65 volts because the 86' runs like champ and that is what it was at.

Now for the "why the potentiometer influences the KE, is cuz one it influences the extra enrichment during cold start, and after that it signals how far the sensor plate moves as air flow increases as it pass's by when warm.

"As I said before ps2cho, Concentrate on the AFM!"

Idle issues
 

I may be starting to sound like a broken record on my posts but it is just because it is the only thing that worked on my car. And I do realize the amount of work that you have put into your car. I have followed your posts intently as I am now looking at a head job of my own. And I have to say you have done a wonderful job with the pics and stuff. Keep up the good work. :)
Anyways, back on subject.....;) I was having idle trouble with my 300E and it was the Idle Control Valve..... I didn't see you mention it anywhere in this thread so I am just asking...

Thanks. I always know when I look for other posts on subjects, some high quality pictures really are worth a 1000 words...I'd rather show not tell.

No, but it wouldn't make sense as the ICV opens and closes perfectly fine. I believe the EZL controls the way the ICV opens/closes based on readings from the potentiometer. Also unplugging the ICV did not affect me at all.

If the potentiometer does not pull through, I can always swap the ICV for the hell of it...

I thought the EZL was the ignition module - that shouldn't have any impact on the ICV.

As far as I know, the ICU controls the ICV's movements.

Have you ever taken a look inside your combustion chambers? They (and the valves) could simply be coked up due to age & inferior gasoline. You could try the "sip-in GM top end cleaner" method, or run it at 4,000 RPM for around 20 minutes (it's like putting your oven on "clean" - it pretty much burns off most deposits).

The GM method has worked for me (on other cars), but requires sitting overnight, puts out a buttload of smoke the next day for about 10 minutes, and requires an immediate oil change. The other method just stresses your engine.

Remember, there's a mechanical aspect of your engine, too - it's not all about fuel delivery & spark (though those shouldn't be overlooked).

ICU sorry, you are correct.

Here's my combustion chamber....I got the valves done too :)

http://www.ps2cho.net/downloads/phot...t/rebuild2.jpg
http://www.ps2cho.net/downloads/phot...t/rebuild3.jpg

The only thing I do have is a "ticking" at the back of the engine...I'm not exactly sure what it is though. Its not very loud, but there is a tick.

I am having a similar problem with an 89 300E with 140K miles. This problem would "go away" if I could trick the system to run 100 rpms (if that) higher at idle. The car IMO is not worth the time or effort to go to the trouble the OP has with his car and frankly makes the somewhat minor annoyance of the low idle a daunting problem.

Exactly. As soon as I touch the throttle it disappears even if I give it the smallest amount of rpm's possible. I guess then the potentiometer would make logical sense as its now being controlled by my foot, right?

Thats my thought.

I swear your car was right behind mine in the assembly line. I got a ticking noise coming from the back of my engine too, and it got slightly louder when I had the head rebuilt. I took the head off with cam, and bearings again. Took it to the shop and we both went through it with a fine toothed comb, to find everything in spec. (still can't figure where this noise is coming from:mad:) Could it be the bottom end? wrist pins, rod bearings, somethin along those lines?

It seems You have done a very thorough diagnosis ,leaves only the fuel distributer for further checks . Turn to a lean condition ,test and then a rich condition to determine where it is better. if its rich you may like to check the cold start injector for a dribble leak.
mak
300SE