what is the purpose of the microswitch near the throttle linkage?

mine is has recently broken - the arm that presses on the switch broke, but the switch itself is still ok, although it can no longer be activated by the throttle linkage. As a result, my idling speed is very high on startup if the engine is cold. This was pointed out to me by my mechanic, and on startup, I sometimes need to manually activate the switch just to get the idling back to somewhere near normal.

I also noticed that my engine's torque is not so good in the midrange, and when I give it the boot, I sense irregularities in the torque curve, as the engine winds itself up under load. My guess is that this could also be related to the microswitch, because I noticed this only recently.

mine is an M103 2.6 engine.

It tells the engine management computer if the throttle is at idle or full acceleration. So if the switch position is does not reflect what the throttle is doing, your EHA is trying to respond to faulty data. Like it may think you are wide open and go to full enrichment when you are just driving normally.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Actually I think he is referring to the decel switch and I'm not sure what it does overall. I suppose its intended purpose is to signal closed throttle fuel fuel cut-off under deceleration.

It also plays a part in closed throttle recognition for idle control. I've never been exactly sure why they needed a second idle recognition switch when they also had the throttle switch doing the same thing.

I'm guessing this is what is being talked about as the throttle switch is not visable until disassembly.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Corrected.

I was looking at the decel micro switch, and the diagram shows a "Full Load" position. But upon closer examination, that position has no connection to the control unit.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

"I was looking at the decel micro switch, and the diagram shows a "Full Load" position. But upon closer examination, that position has no connection to the control unit."

You are looking at the decel microswitch on the car, and the throttle position switch on the schematic. As Steve said, these are different items, in different locations. The TPS is bolted to the side of the throttle body, at the butterfly shaft. The decel microswitch is on the throttle linkage, near the accelerator cable.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Nope, this came off right off the the schematic on the CD (S27/2) . Send me an email if you want a copy.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Ok. Send the part of the schematic that shows both the decel switch and both switches in the TPS. I would be curious to see what is going on here.

Steve
aq433 at hotmail dot com

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Ctaylor, thanks for the schema. However, it says just what I did - the decel switch shows just one closure, while the TPS has two - one for full throttle, and one for idle. The TPS is NOT the microswitch on the linkage - that is the decel switch. The TPS is bolted onto the side of the throttle body itself.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7