Throttle Microswitch

Hey guys,

What does the throttle microswitch do and what are the symtoms when it is bad? I was advised that mine was bad and needs replacing. The car is running like crapola.

Thanks

Jimmy
1988 Benz 300e

[AusMBtech]

The microswitch is just there to provide an idle throttle position signal for idle control and fuel shutoff on decel.

This won't give an effect of a general rough engine running. What are your symptoms?

A simple check of the switch is to check for an open/closed circuit when the switch is open/closed.

Hey AusMBtech,

Hmmm... When I give the car gas sometimes it will go just fine other times it will stumble, spit and sputter. If you feather the throttle it sometimes will do fine but take off normaly and you get the spit and sputter. If you floor it it will try and die.

[AusMBtech]

Just sticking to fuel delivery faults it sounds like it's running lean on acceleration.

High control pressure, EHA not working, general lean running, carboned up valves (yep, it'll do it) can all cause these problems.

If you have terminal 3 in your diagnositic connector then check your lambda value first. 50% is normal for most engines but the 103 engine (which I presume you have) prefers to run at 30-40% (I put it on 35% during services), they run quite well at this mixture, 50% is too lean on acceleration from experience. You can check you EHA (if fitted) for operation by watching the lambda value fluctuate +-5%.

A can of carby cleaner down the intake on a hot engine will also help if you haven't done it in a while. Make sure you do it on a hot engine and try and keep the lowest rpms possible without stalling (to help saturate the carbon and make it break off the valves).

Give those 2 remedys a go since they are simple and don't require much in the way of tools.

I will give those a shot this weekend and see what happens. Thanks for the advice. Hopefully it fixes as I am getting gray hair messing with this thing

Hey AusMBtech,

I was messing with the #3 pin on the x11 do I need to unplug the purge line when testing? If so where is it at? Here is where I got that from http://www.landiss.com/mixture.htm

I should have some #'s tomorrow.

Thanks for all the help. Hopefully I can have this thing back on the road here soon.
Thanks

Jimmy