1990 500SL with ASR is in limp mode as soon as I start the car. It revs with pedal, but stalls when linkage moved by hand?!
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 installed 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?

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Regards,
James

This trans is a 722.3 with full hydraulic control, however , there is a solenoid on the trans that dumps governor pressure ( road speed ) when the car is cold so the trans shifts later to warm up the cats. There might be a problem with that circuit.

Past that I don't have much experience with that era car.

I went through this on my 93 SL500. it drove me nuts. I walked away for a bit, but do make sure your cap and rotor are clean(do not assume). Use a dremil and sand paper to make sure everything is clean, and that should solve your backfiring...

Some of these cars have switch on pedal, and the switch works the moment you push on the throttle. The switch may short, or not work. My buddy with his 93 W140 had two or three of these replaced at the MB Dealer in the late 90's. The switch on the bottom of the carpet can short closed(sorry I cannot remember the name of it). It trips when you do a wide-open-throttle. Make sure you can manually toggle it, and measure the continuity with a ohm meter...

Martin

My suggestion? Take the car to Blue Ridge MB in Lilburn. Jono knows MB V8's and he will get it running properly for sure.

Rgds,
Chris W.
former '95 E300D, 467K

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