Idle or full throttle
 

I have an 86 300E that has an issue with the throttle. When cruising at about any speed, the throttle feels like it just falls. Without moving my foot the throttle will flutter, quite badly sometimes, or just die off and then kick back in. If I go to wide open throttle, she will run there all day, or just off idle it does fine. But through the midrange of the pedal it fells like it is has short-timers and doesn't know where it is supposed to be. I was thinking that maybe the TPS is wearing out in the midrange. Any insight would be appreciated.

Interesting problem!

On a 300E (assuming it's the 3.0 12 valve here), it's electro-mechanial injection. Generally fuel is injected due to the air flow meter (the big metal flap in the intake) moving down, as it mechanically moves a plunger and allows fuel to flow. Well that's approximately as I understand it. The "TPS" sensor is not really a TPS but an potentiometer connected to the above mentioned flap... it's an air flow sensor. This lets the computer know the air coming in, and that information is used to provide smaller tweaks to the mixture, via the EHA.

If you try disconnecting the EHA, this pretty much removes the ability of the computer to affect the mixture of the car. Which would mean the readings from the "TPS" are contributing to nothing. In this mode the car should not have the problem you describe.

I hope that makes sense, it's hard to word it right!

Other things on the throttle are the WOT/no throttle switch in the base of the throttle body, and the 'engine deceleration' switch on the throttle linkage. Could be worth testing these including the wiring back to the ECU (i've heard it can go bad) as one of these activating when it shouldn't might cause what you've got?

Good luck...

Well that helps me understand the system a little more, I ordered a manual and it hasn't arrived yet so I'm kinda shootin in to the dark. I will look into that system though, thanks for the insight.