My wife's '90 300D has poor acceleration. It just started.

I changed all of the filters. I checked the hose to the alta valve.

The safety control valve is energized as soon as the car is started. When I by pass it it runs as it should.

Does anyone know how to test the electric portion of the system?

Thanks

Dwight Hanson

if you mean the switchover valve mounted on the inside left front fender it may be that the switch on the intake manifold has failed in the closed position.I think that would be an unusual failure but nothing is impossible.You will see the switch on the side of the intake manifold,it has 1 wire on it and is about a one inch hex,disconnect the wire and see if that makes a difference,if it does the switch is the problem,if not then the circuit that that wire connects to has become grounded somewhere.You will need a wiring diagram to locate the problem as that wire is connected to some other components besides the switch(at least it is on my 91 and i think they are the same).I hope for your sake it is that switch as it would be a simple fix,troubleshooting the rest of the circuit will be a bit more complicated. My$.02 Don

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Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles

Thanks for the reply!

I checked the switch and it is open. The wiring diagrams I have are not very good. I have a manual coming which I hope helps.

I was reading on a site that there is a coolant temperature transducer. I assume this changes resistance at the temperature changes. I think this is the likely candidate. I need more information to test it and other parts of the circuit.

Dwight

Do a search for problems related to the 124.128 and you'll find way more than you can read on the engine control system. One thing I can tell you is build a code reader/clearer. The parts only cost about $20 from Radio Shack, and it's easy to build if you know how to solder. Plans/schematic can be found here... http://pages.prodigy.net/jforgione/MB_X11.html (scroll to the bottom).

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Dale

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1990 300D 2.5 Turbo -155k
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