It's been a long time since I replaced injectors, but as I remember there is a rubber seal, then a plastic holder, then a rubber 0-ring. I think I replaced both rubber pieces, reusing the plastic holder, which seemed fine.

If you are pulling the injectors, which seems like a good first fix attempt if spraying around them definitely causes changes in the idle, then you might try to move the hard fuel lines around, and hook up the injectors outside the engine, where you can check for leakage. Just turn on the pump for a few seconds and see if one drips gas. Obviously use precautions like a cool engine, fire extinguisher handy, etc.

So, it seems the idle starts out okay, then goes so lean the EHA can't compensate, then catches and goes back to normal.
Can't come up with a way an idle leak could cycle like that. And since pulling the EHA allows it to still happen, but not heal, then maybe it's a fuel delivery problem in the fuel distributor. Maybe a leak around the air valve piston that leaks down to a certain point, then the engine tries to recover and opens the IAC further, forcing the air valve to change position and clear it up awhile, then it starts all over again.

Just guessing of course, but it might point to trying to measure the EHA current as the cycle happens, and also measuring the low=side pressure to see if it drops during the go-lean cycle.

DG

With KOEO, EHA current reads .89 mA's. That's not right - I think it should be around 20 mA's...? Pulled the OVP and mA's are now 0 with KOEO - which if I understand the wiring properly, is correct. BTW, the OVP rattles some and is the original, so I'm going to replace it.

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

My '91 103 reads 20 ma with KOEO, so you may be on to something.

An interesting EHA observation I made one day: when warm, as soon as the engine is started, the EHA reading then jumps to the last setting it was at before it was turned off (in the 1-2 ma range, if Lambda is set pretty well). So it seems to have a mamory of where it should be with a warm engine, even before it goes closed-loop. From that, I deduced that setting the lambda either rich or lean to aid warm starting may not help much, because the EHA cuts right in immeditely on a warm start and mimics the previous closed-loop operation.

DG

Could the air intake temperature sensor in the air boot (late m103 only) be the cause of the intial startup hesitation? Never been able to figure out exactly what the AIT influences (ICV, EHA, ???)

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http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...

OK, some updates..

I used another multimeter today and checked the EHA current again - since I have a '91 300CE with basically the same system, I was able to compare results.

Using an older Sears multimeter - model 82015 - I was able to get 20 mA's at the EHA in my 300CE with KOEO. For some reason, I guess I can't figure out my newer Sears that I bought with the duty cycle feature - model 82139. With it, I initially got 2.72 mA's - I think...?

Using the older multimeter with my 560SL, I get 75 mA's with KOEO (According to the FSM 07.3-121, 75 mA's is correct with KOEO) - once the engine starts to warm up it drops back down and hovers around 0. I have noticed a hissing noise, air escaping from around the air sensor plate. I decided to try and adjust the mixture - after some fiddling I got the duty cycle to hover around 50% and the EHA current to center around 0 mA's. The idle evened out and isn't nearly as "rhythmic" and the duty cycle does not go to 90%+ now - BUT, the idle speed has increased some, to about 900 rpm in park and 750-800 rpm in gear.

Am I getting closer?

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

OK. Sounds like the EHA is doing OK.
If it won't idle down, then it would seem the IAC is not adjusting properly, or it's turned all the way down and you have a stuck throttle blade or a bad vacuum leak. There is a simple way to get the EHA to close all the way, disconnect it while it is running, or not running or something - I can't remember right off. But I have done it, and then checked the idle speed from just the throttle blade opening. It idled about 500 with the IAC closed, so my throttle blade must be about right.
There is an adjustment screw on the throttle blade, just like an old carb.

To idle fast, it has to be getting air somewhere: throttle blade, IAC, or a vacuum leak are the main suspects I suppose.

But, all you did to get the fast idle was mess with the air meter arm, right?
So, maybe it leaned out and sped up? but the EHa says it's pretty right according to the signal from the O2 sensor.

hmmmm. more stuff to try.

DG

I turned the mixture screw using my 3mm wrench - mostly CCW, which dropped the duty cycle down in the 30-40% range. This effected the idle too much - too slow...so I adjusted it CW. Got it to even out with duty cycle in upper 50's, but idle was too fast - probably 1100 rpm's. So I brought it back down - CCW - to where I am now.

I don't know if I can adjust the IAC valve - I did unplug it and idle really speeds up and I hear a serious air leak. What do you mean by the throttle blade? I am thinking I need to adjust the air sensor plate...

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

The throttle blade is underneath the air sensor plate, and controlled by the throttle linkage. It has a stop screw on it that allows a small bit of air to pass thru at idle. Just like an old carburator. The IAC adds the rest of the air, depending on need. If the throttle blade is too far open when the accelerator pedal is closed at idle, then the IAC valve cannot adjust the air flow down enough. With my IAC completely closed or blocked off, the engine idles at 500 RPM with the air sneaking past the barely open throttle blade.
then the IAC comes on and adds air to achieve the 600 RPM idle with the AC on and the tranny in Drive.
may not be it, but worth a quick check.

DG

Is this the "lambda tower" as some refer to it? My SL had a COLD starting issue and a stumble for a few secs after start. Cut out the "plug" and it's a new car now

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former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL

I had simlar issues with the idle rhythmically going up and down after starting. The problem truned out to be the idle control valve was bad even though the reference check was good. If I jumped it with battery voltage and all those amps the valve could be geard clicking with on and off as I touch the battery positive post with jumper cable. My car was having difficult start cold or hot. Try used ICV.

Will, sorry for late reply.
no, the lambda tower is the projection with the plug in the top that houses the adjustment screw for the big air valve in the top of the throttle body.
This throttle valve or valve is not connected to the accelerator pedal, but is moved down by the air being drawn around it. The actual throttle blade or valve is directly nuder it about 4 inches, and is totally controlled by the accelerator pedal cable and your right foot. Thats the adjustment I was referring to above.

Oh, IAC can certainly affect uneven idle speed if it is not functioning freely.
It's just a little rotating cylinder with a slot in one side, turned by a stepping motor.
A quick fix might be to pull the IAC unit off and spray it liberally with a cleaner or even WD40. I actually blast mine with WD40 and then drip a little oil on the rotator every couple of years; so far so good.

DG