1990 500SL revs with pedal, but stalls when linkage moved by hand?!

[JamesO]

Hello all, I am perplexed by my 1990 500SL euro build, that will allow the revving of engine using pedal(not alot of power), but will stall when manually moving linkage at engine firewall. Let me give basic history. Car recently serviced few months ago, rotor and cap bad. Fast forward to starting one morning like a truck, one bank firing, unburnt gas smell. I found a leaking coil. Changed both coils, new caps, rotors, plugs and wires. Same problem persists. Feels like limp mode. Contacted a parts guy I know, I install a throttle potentiometer into the linkage along the firewall. It now fires on all pistons, very faint unburnt fuel smell, but no power and feels like limp mode. I now go down the list of what will cause this. I changed brake pedal switch. I went into the plastic housing box where the computers live and there are 4 blue and white wires on a screw post. I changed them out off the screw one at a time as one will control ASR. I found that 2 of the wires caused the yellow triangle to light as well as tire symbol to light on console. I have tried what Bob Terry suggested by sticking something in the V-shaped linkage that leads to the actuator linkage to remove the "play". To no avail.
I am thinking there is a vacuum leak? Starts, Idles fine, no power and won't shift(limp mode) At wits end!? Suggestions please?

[optimusprime]

If i am right your throttle is electronic. And after a time they need rebuilding .This is a specialist job. Take a look on YouTube. Can you rermove the air filter , then ask someone to start the engine up .Then the throttle flap should move or open up , if you use the linkage .If not it will want a rebuild...Please let us know what you find .

[ILUVMILS]

I'm assuming the vehicle in question is equipped with ASR. If you move the throttle by hand the position sensors disagree and the throttle goes into limp mode. If you MUST manually operate the throttle do it from the cruise control actuator and you'll avoid the issue.......I wouldn't mess around having the actuator re-built just yet

[JamesO]

Yes, the car is ASR equipped. The cruise control has never worked on the car.

When I start the car it is already in limp mode...

[JamesO]

i do have a built in "S" and "E" switch in the shift lever area. I moved the it to "S" mode starting in 1st gear and it does in fact shift up thru the gears. So now I don't believe it is limp mode or asr related....just no power, running rough. It idles fine. I can get it going 60 mph or more......